#### Answer

x = 15

#### Work Step by Step

0.40x + 0.24(20-x) = 0.36(20)
Multiply both sides by 100 to clear the equation of all decimals.
40x + 24(20-x) = 36(20)
Use the distributive property.
40x + 480 - 24x = 720
40x - 24x = 720 - 480
16x = 240
Divide both sides by 16.
x = 15