42 IS 21% OF WHAT NUMBER

For this case we can make use of the following rule of three:

42 -----------------------> 21%

x -------------------------> 100%

In this case we have the following variable

x: unknown number whose 21% is equal to 42-

From the rule of three we clear x.

We have then:

42 is 21% of 200

yes yes yes yes yes yes yes yes yes