144 is 15% of what number

The simplest way I've found is to find 1% and multiply by 100.

15% / 15 = 1%

so

144 / 15 = 9.6

now multiply by 100 (or move the decimal place to the right (because multiplying) two places (the number of zeros))

9.6 x 100 = 960

Answer: 960