it's a i think, hope this helps
The ratio of volumes is equal to the ratio of the cubes of the scale factor. Thus,
Volume ratio:
6³ : 7³
216 : 343
5x + 2y = 7 . . . (1)
y = x + 1 . . . (2)
Putting (2) into (1) gives
5x + 2(x + 1) = 7 => 5x + 2x + 2 = 7 => 7x = 7 - 2 = 5 => x = 5/7
From (2) y = 5/7 + 1 = 12/7
Therefore, solution is {(5/7, 12/7)}
Paul surely charges 75 dollars, and then he adds 40 dollars per hours. This means that the expression for the money he asks is

where
is the amount of money and
is the number of hours.
Since
can be at most 8, this is the case that generates the highest money, so if we plug
we have
