Susan's cell phone allows her to use 960 minutes per month with no additional charge. She has 188 minutes left for this month. How many minutes has she already used this month?

If Susan had a total of 960 minutes to use, and currently she has 188 minutes left then you would subtract 960-188 to get the amount she already used.

960-188=772

To check the answer, you would add the amount she used (772) to the amount she has left (188) to get the total she had at the beginning of the month. 772+188=960