Hi there!
To solve is pretty easy. First, simplify.
21/4=(1/2x+3x) -> Combine Like Terms
21/4=7/2x
FLIP
7/2x=21/4
Multiply both sides by 2/7.
(2/7)*(7/2x)=(2/7)*(21/4)
x = 2/3
Hope this helps!
Volume = area of base * height = 1/2 * 6 * 8 * 12
= 288 ft^3 answer
Use the ticket price in the first column in the formula 400-7p to get the answer for the second column (number of tickets sold)
Then multiple the number to f tickets in the second column by the price in the first to determine the revenue.