Answer :

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:

[tex] x = (\frac{100}{21}) * (42)

x = 200
[/tex]

Answer:

42 is 21% of 200