The total amount y (in dollars) in your savings account after buying x video games is represented by y=90-10x. You have $40 in your account after buying video games. How many video games did you buy?

5 video games bought.

Explanation:
Step one) identify all variables.
> y = money in bank acc AFTER buying (x) video games.
Step two) y = $40
Step three) substitute
> 40 = 90 - 10x.
Step Four) solve for x
> subtract 90 both sides.
-50 = -10x
DIVIDE by -10 on both sides ( to isolated x)
This equals 5 = x
x is number of video games bought meaning >> 5 video games bought :))

The answer would be (c)