Derrick, John and Kenneth had a total of 720 stickers. Derrick used 20% of his stickers, John used 80 stickers and Kenneth used twice as many stickers as Derrick. They had 448 stickers left. How many stickers did Derrick have at first?

sugabreaddoughman Oct 11, 2023

#1**+1 **

D + J + K = 720 ⇒ J + K = 720 - D (1)

Derrick used .20D and had .80D left

John had J - 80 left

Kenneth had K - .40D left

.8D + J - 80 + K - .4D = 448 simplify

.4D + J + K = 448 + 80 ,...... sub in (1)

.4D + (720 -D) = 528

-.6D + = 528 - 720

-.6D = -192

D = -192 /( -.6D) = 320 = number Derrick had at first

CPhill Oct 11, 2023