Eight and eighty-four hundredths in standard decimal form is 8.84 because 8 is the whole number, the 8 on the right of the decimal is in the tenths place, and 4 is in the hundredths place. :)
4(2x +5) = (8x + 20)
8x =20 is an equivalent expression
245/8.2 = 416/x
245x = 3411.2
x = 13.9
So the answer is 13.9 gallons