Iwas given this problem in math and can’t figure out how it’s solved. 21 is 70%of

The answer is 30

Step-by-step explanation:

Given:

21 is 70%of ___

Let, in the place of blank to solve.

So,

.

Multiply both sides by .

.

Now, dividing both sides by .

.

So, the value of .

Therefore, the answer is 30.

225x²+4=0

225x²=0-4

225x²=-4

x²=-4/225

x=±√-4/225