correction: Doug spent $90 over the week end. He spent 1/4 of it on a CD and 1/5 on movie ticket. how much money did he have at the start of the weekend?
let his amount be $x
(1/4)x + (1/5)x = 90
times 20 , the LCD
5x+ 4x = 1800
9x = 1800
x = 200
or
he spent 1/4 + 1/5 of his money
= 9/20 of his money
this is $90 , so 90 รท 9/20 = 200