Question

Blake has a total of 64 DVD's and CD's. If the number of CD's is eight more than three times the number of DVD's, how many DVD's does he have?

Answer 1

Well we have a system of equations here

dvds + cds = 64 right?

D + C = 64

and the numbers of cds (C) is 8 more than 3 times the dvds (D)

C = 3D + 8

what would we do from here?

Answer 2

Let the number of DVDs = x
and the number of CDs = y
According to the question
x+y=64, Therefore x = 64-y
y=3x+8
Now substitute x value
y = 3(64-y)+8
y=192-3y+8
3y+y=200
4y=200
y=200/4 = 50
Number of DVDs = 64-50 = 14
Number of CDs = 50