Question

The temperature decreased from 71.5*F to 56.8*F overnight. How much did the temperature drop?

Answer 1

You use subtraction:
71.5*F- 56.8*F= 14.7*F
Hope this helps~

Answer 2

The word decreased shows that you need to use subtraction for this problem.

Take 71.5*F - 56.8*F = 14.7*F that the temperature dropped