Answer:
For this problem, we need to add to the price of the phone (50 $) the cost of the data usage (which is 0.20 $ per minute).
If he spends on average 200 minutes, we can calculate what that costs by multiplying the number of minutes by the cost of each one: 200 * 0.2 = $40
And we can now add to the $50 the $40: 50 + 40 = $90
