Question

you were charged $51.50 last month for data usage on your smartphone. your data plan charges a monthly fee of $20 plus $2.50 for each extra gigabyte used. how many extra gigabytes did you use last month?

Answer 1

I think the answer is 12.6 extra gigabytes because:

20 - 51.50 = 31.50

31.50 / 2.50 = 12.6