Let x = the unknown number.
Because three-sevenths of the number is 21, therefore
(3/7)x = 21

That is
(3x)/7 = 21

Multiply each side by 7.
3x = 21*7 = 147

Divide each side by 3.
x = 147/3 = 49

Answer: 49

6 0

3 years ago

Help ! I don’t know if I have it correct. Can somebody check it out. I got 81/65536 which I know has to be incorrect.

Anna35 [415]

<h3>Answer: 9</h3>

Work Shown:

In the numerator, we have 2^2*x^2, which is really just 4x^2. Replace x with 3 and we get 4*x^2 = 4*3^2 = 36.

For the denominator, xy^2, we get

x*y^2 = 3*2^2 = 12

So far we have,

$\frac{2^2x^2}{xy^2} = \frac{4x^2}{xy^2} = \frac{36}{12} = 3\\\\\text{ or simply} \\\\\frac{2^2x^2}{xy^2} = 3$

when x = 3 and y = 2.

Square both sides to end up with...

$\frac{2^2x^2}{xy^2} = 3\\\\\left(\frac{2^2x^2}{xy^2}\right)^2 = 3^2\\\\\left(\frac{2^2x^2}{xy^2}\right)^2 = 9$

6 0

3 years ago