Set up a proportion
EA / EB = ED/ EC
16 / (5x + 2 + 16) = 12 / (12 + 24)
16/(5x + 18) = 12 / 36 Cross multiply
16 * 36 = (4x + 18)*12 Remove the brackets
576 = 48x + 216 Subtract 216 from both sides.
360 = 48x Divide by 48
360/48 = x
7.5 = x
The water bill was 1/5 of the total, so was 0.2*$540 = $108.
Solve the literal equation 2xy - xz = 4 for x
x = 4/(2y-z)
y =/ z/2
