The first two sentences compare sales of cameras and computers to TVs. There is no reference point in relating cameras sales to computer sales. Therefore, we do not have enough information to determine whether the store sold the same number of cameras as computers. The answer must be uncertain.

Let's look at each sentence numerically. 

This means that Grade 1 MUST be larger than Grade 2. Sentence 3 states that there are more 2nd graders than 1st graders at Lincoln Elementary. This statement must be false.

Let's put the information we know on a spectrum, with the person that owns the most animals on the extreme left and the person that owns the fewest animals on the extreme right. Sentence 1 tells us that Andrew owns fewer animals than Jason. This means that Jason owns MORE animals than Andrew. 

MOST                 FEWEST

Jason     --         Andrew

Sentence 2 tells us that Dennis owns fewer animals than Andrew. Therefore, Dennis should be placed to the right of Andrew.

MOST                       FEWEST

Jason   -- Andrew  -- Dennis

Sentence 3 says that Jason owns more animals than Dennis. Looking at the spectrum above, this statement is true.

Based on the information in the first two sentences, we know that Todd is a slower swimmer than both Alicia and Jordan. We do not have a direct comparison of Alicia and Jordan's swimming speeds. This means that the truthfulness of the third sentence is uncertain.

All three sentences are comparing different attributes of the three dogs. Although we know that Riley is stronger than Kelsey, we do not have any comparison of their speed except in the third sentence. If we only know that the first two sentences are true, the truthfulness of the third sentence is uncertain.

Let's place each child on a spectrum based on how many stuffed animals each has. The child with the most stuffed animals will be placed on the extreme left side of the spectrum and the child with the fewest stuffed animals will be placed on the extreme right side of the spectrum. From Sentence 1, we know that Shelley has more stuffed animals than Bert, so Shelley should be placed on the left, and Bert on the right of the spectrum.

MOST                            FEWEST

Shelley          --             Bert

From Sentence 2, we know that Bert has more stuffed animals than Tanya, so Tanya should be placed to the right of Bert on the spectrum.

MOST                            FEWEST

Shelley    --    Bert   --    Tanya

Looking at the spectrum, we can now tell that Sentence 3 is true: Tanya has fewer stuffed animals than Shelley.

Let's arrange the three people on a spectrum: the person that has read the most books goes on the extreme left and the person that has read the fewest books goes on the extreme right. From Sentence 1, we know that Jeremy has read more books than Leah.

MOST                    FEWEST

Jeremy       --        Leah

From Sentence 2, we know that Daniel has read more books than Jeremy, so Daniel should be placed to the left of Jeremy on the spectrum.

MOST                    FEWEST

Daniel -- Jeremy -- Leah

This means that the Sentence 3 is true: Daniel has read more books than Leah.

There is not enough information given in the first two sentences to determine if Selina loves the color red. We know that she hates pastel colors and that pink is a pastel color, therefore, Selina hates the color pink. Although red is not a pastel color, there is nothing stated in the first two sentences about colors Selina likes. Consequently, it is uncertain whether she loves the color red.

Based on the information from the first two sentences, the third sentence must be false. Sentence 1 states that Magali will take her vacation "as soon as" she has earned the money. This implies that Magali will not wait, but will go on vacation immediately. Sentence 2 states that Magali is working an extra job to earn the money more quickly. This sentence also implies that Magali has not earned enough money yet. Consequently, the third sentence stating that Magali has earned enough money to go on vacation must be false.

Since we only know that the first two sentences are true, the truthfulness of the third sentence is uncertain. The first two sentences compare the popularity of peanut butter and jelly sandwiches with tuna sandwiches. Roast beef is never mentioned in the first two sentences, so we can not determine if it is the most popular or not.