To evaluate an expression we make substitutions into the expression

2(x – 3) + 5y² becomes 2(2 – 3) + 5 * 3² = –2 + 45 = 43

Use the first equation to solve for x, then plug into the 2nd equation to find a value.

5x³ = 40

x³ = 8

x = 2

12(2) – (2/2) = 24 – 1 = 23

Upstream:        p – w = (10/2)    or     p – w = 5 miles/hour

Downstream:    p + w = (27/3)    or    p + w = 9 miles/hour

Then we add the two equations together to cancel out the w's. After adding we see

2p = 14

p = 7 miles/hour   where p is the rate of the paddling. We plug p into the equation to find

w = 2 miles/hour    where w is the rate of the stream's water.

The answer is 23. 

Since Rachel and Claire are twins they are the same age. We will use the variable r to represent both Rachel and Claire's ages. 

From the question we can form two equations. They are:

t = r + 2       and     65 = t + 2r

lets plug the first equation into the second to solve for r.

65 = (r + 2) + 2r

65 = 3r +2

63 = 3r

r = 21      This means Rachel and Claire are 21 years old. Plug this into the equation so

t = 23       Tim is 23 years old. 

It's easiest if we convert all percentages to actual oz of water for each step here. As such, 35% of the 80 oz of drink B would have 0.35(80) = 28 oz of water in it. 

We can set up an equation that similarly converts each "percentage of a fixed weight of liquid" to ensure that our final weight is equivalent to 30% to the sum of drink A and B. On the left side, the fixed values are the percentages of each drink individually, and on the right side is what the question requires as a fixed percentage of the final weight:

0.2(A) + 0.35(80) = 0.3(A + 80)

0.2A + 28 = 0.3A + 24

A = 40 

Solving for A, we get 40 oz of A that must be poured into B. You may plug this back into the equation to check it.

First, we need to evaluate 5&3.

Since x&y = xy – x + y, we can find 5&3 as follows:

5&3 = 5(3) – 5 + 3

= 15 – 5 + 3

= 13

Now, we need to go through each of the choices and determine which one equals 13.

Let's start with 2&(8&1). Remember that we must first evaluate inside the parantheses.

2&(8&1) = 2&(8(1) – 8 + 1)

= 2&(8 – 8 + 1)

= 2&(1)

= 2(1) – 2 + 1 = 1, which doesn't equal 13.

Next, let's evaluate 4&(3&4).

4&(3&4) = 4&(3(4) – 3 + 4)

= 4&(13) = 4(13) – 4 + 13 = 61.

Next, we can evaulate 8&(2&0).

8&(2&0) = 8&(2(0) – 2 + 0)

= 8&(–2) = 8(–2) – 8 + 2 = –22.

Next, let's find 3&(5&2).

3&(5&2) = 3&(5(2) – 5 + 2)

= 3&(7) = 3(7) – 3 + 7 = 25.

Finally, lets evaluate 11&(0&2).

11&(0&2) = 11&(0(2) – 0 + 2)

= 11&(2) = 11(2) – 11 + 2 = 13.

The answer is 11&(0&2).

Just take this step by step.  First write out each equation:

x = 0.75y

y = 8(1.5z)

First, simplify the second equation:

y = 12z

Then, substitute y from this equation into the first:

x = 0.75(12z) = 9z

The key to solving this question is noticing that we can factor out a two:

2x + 6y = 44 is the same as 2(x + 3y) = 44

Therefore, x + 3y = 22

In this case, x + 3y + 33 is the same as 22 + 33 or 55

Let's make 3 equations based on our data:

J = 4S + 4

P = 3J

S = 20

All we have to do is sequentially replace values.

Substitute 20 for S in the J equation:

J = 4 * 20 + 4 = 84

Now, we can calculate P: P = 3 * 84 = 252

Rewrite our question as a set of equations:

R + G + B = 42

R = 42/2 = 21

Therefore, we already know:

G + B = 21

Also, we know that B = 5 + G

Replace that value into the B + G equation:

G + 5 + G = 21 → 2G + 5 = 21 → 2G = 16; G = 8

Therefore, we know that there are 5 + 8 or 13 blue marbles.

The total is therefore 21 Red, 13 Blue, 8 Green