What is 9 divided by 16 minus 9 divided by 20 equal?

This is subtraction of fractions.

Hence

9/16 - 9/20 =>

[9(20) - 9(16)] / (16 x 20)

[180 - 144] / 320

[36] /320

Cancel down by '4'

9/80 The answer ; this will not reduce any further.