Question

Three-sevenths of a number is 21. Find the number.

the number is 9
the number is 27
the number is 49

Answer 1

3/7 of the number is 21.

1/7 of the number is 21 / 3 = 7

7/7 of the number is 7 * 7 = 49

The number is 49.

Check: 3/7 * 49 = 21.

Hence, the number is 49.

Answer 2

let The number be x

Acc. to question...
$\frac{3}{7} x = 21 \\ > > 3x = 21 \times 7 \\ > > x = \frac{21 \times 7}{3} \\ > > x = 7 \times 7 \\ > > x = 49$
So,49 is your required number!

Hope it Helps..
Regards,
Leukonov.