Answer:
They sold 10 videos and 30 CDs
Step-by-step explanation:
So, you need two different equations-
We will use c to represent CDs and v to represent videos
So-
c + v = 40
4c + 6v = 180
Single out a variable in the first equation-
v = 40 - c
Because this is equal to v, insert it where v is in the second equation-
4c + 6(40 - c) = 180
Multiply-
4c + 240 - 6c = 180
Solve-
-2c + 240 = 180
-2c = -60
c = 30
Now that you know c, use first equation to find v-
30 + v = 40
v = 10
So c = 30 and v = 10
