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