Pencils are sold for $0.23 each.

If Susie buys 7 pencils, she is paying

7 x $0.23 = 

$1.61 for pencils.

Notebooks are sold in pairs (or in packages of two), for $3.04 a pair. 

If Susie buys 8 notebooks, that means that she bought

8 ÷ 2 =

4 pairs of notebooks.

So, 4 pairs of notebooks, at $3.04 a pair costs

4 x $3.04 =

$12.16. 

Susie also buys a dozen, or 12, folders. Folders come in packages of 4.

This means that Susie buys

12 ÷ 4 = 

3 packages of folders.

Because each package costs $2.12, Susie pays

3 x $2.12 = 

$6.36 for a dozen folders.

If we add up the total cost of the pencils, notebooks, and folders we get 

$1.61 + $12.16 + $6.36 = 

$20.13.

Because Susie pays $25, she will be left with 

$25 – $20.13 =

$4.87 in change.

$\displaystyle (-2)^2 + (6)^2 = 4 + 36 =40$

The order of operations states that we must begin solving the mathematical expression by evaluating numbers in parentheses. In this expression, $\displaystyle \small (7-3)$ is in parentheses. When we solve this, we get $\displaystyle \small 4$. Our expression can now be rewritten as:

$\displaystyle \small 5 + 4 \cdot 4$

The order of operations states that the next step would be to evaluate any term with an exponent. Since there are no exponents in this expression, we move on to multiplication. In this expression we are asked to multiply $\displaystyle \small 4\cdot 4$, which is $\displaystyle \small 16$. Our expression can now be written as:

$\displaystyle \small 5+16$

The order of operations would have us divide next, but seeing as there is no division in this expression, we move on to addition. $\displaystyle \small 5+16 = 21$.

There are six parcels of equal size; the total size is therefore the product of the common size (510 acres) and the number of parcels (6). This is $\displaystyle 510 \times 6$

Substitute 7 for $\displaystyle x$. 

$\displaystyle 5x - 4 = 5 \times 7 - 4$

By order of operations, multiply, then subtract.

$\displaystyle 5 \times 7 - 4 = 35 - 4 = 31$

To multiply two numbers of unlike sign, multiply their absolute values, then affix a negative symbol in front:

$\displaystyle 13 \times (-7) = -(13 \times 7) = -91$

To multply two negative numbers, just multiply their absolute values; the product will be positive:

$\displaystyle -4 \times (-17) = +(4 \times 17) = 68$

Substitute 8 for $\displaystyle x$. 

$\displaystyle 5x +7 = 5\cdot 8 +7$

By order of operations, multiply, then add.

$\displaystyle 5\cdot 8 +7 = 40 + 7 = 47$

When multiplying two negative numbers, the product will be positive. The correct answer is 324.

The equation has multiplication, so the story must have multiplication as well. Ignore the stories which just add or subtract candy bars.

The right answer involves boxes of candy bars:

$\displaystyle 8 \textup{ boxes of candy bars} \times \textup{ 5 candy bars}=40 \textup{ total candy bars}$