Question

6 is what percent of 40?

Answer 1

6 is what percent of 40?

Proportion: 

$\frac{6}{40}= \frac{x}{100}$
x = ?

6 × 100 = 600
600 ÷ 40 = x
600 ÷ 40 = 15
15%

6 is 15% of 40.

Answer 2

For this question you can say: 
6/40 = ?/100
so ? is your answer which is the percent:
6*100/40 = 15% :)))
i hope this is helpful
have a nice day