Liter is used to measure volume
Answer:

Step-by-step explanation:
when multiplying exponents, as long as the base is the same, you add the power. 
1 and 5, 3 and 7, and 4 and 8
(8x-9) + 3x = 90
8x + 3x -9 = 90
11x = 99
x = 99/11 = 9
3x = 3(9) = 27
8x-9 = 90 -27 = 63