So for this we will be using a system of equations, with one equation representing Shakira's sales and the other representing Jeff's sales. Our equations are such (Let x = oranges and y = grapefruit)

For this, I will be using the elimination method. So firstly, multiply both sides of the second equation by -4: 
Next, add 5x+8y=235 and -12x-8y=-340 to get -7x = -105 . From here we can solve for x.
For this, just divide both sides by -7, and your answer is going to be x = 15.
Now that we know what x is, just substitute x for 15 in either equation to solve for y. For this I will be using the second equation.

Since we know that oranges cost $15 and grapefruit cost $20, just add them together to get your answer, which is $35.
Parameterize the line segments (call them
and
, respectively, by


both with
. Then



$15/1 hour= $15/60 minutes= $0.25/1 minute (did this by diving 15 by 60)
Let d be the number of days and h be the height
h = 13 + 0.6d
Answer: (a) h = 13 + 0.6d
Given height = 0.208m, find d:
0.208m = 20.8 cm
20.8 = 13 + 0.6d
0.6d = 20.8 - 13 = 7.8
d = 7.8 ÷ 0.6 = 13
Answer: (b) 13 days
The sides in parentheses times 2 for each is equal to the perimeter expression.