Respuesta :

If 30% of a number x is equal to 21, then x is to 100% as 21 is to 30%:

[tex]\frac{x}{100}=\frac{21}{30}[/tex]

Solve for x:

[tex]x=\frac{21}{30}\times100=70[/tex]

Then, 30% of 70 is 21.

Therefore, the answer is 70.