Question 451559
3x+5(8-x) = 24-x distribute 5 first
3x+40-5x = 24-x 
-2x+40 = 24-x subtract 40 from both sides
-2x = 24-40-x now add x to both sides
-2x+x = 24-40 solve both sides, remember x is the same as 1x
-1x = -16 divide both sides by -1
x = 16

when in doubt always check your answer
3x+5(8-x) = 24-x now substitute 16 for x
3(16)+5(8-16) = 24-16
48+5(-8) = 8
48-40 = 8
8 = 8 

so your answer is x = 16