Question

Three-sevenths of a number is 12. Find the number

Answer 1

49 IS THE ANSWER 
Explanation:

The previous answer, although very thorough, was incorrect.

If the equation is 37x=21 then you can simply multiply both sides by the denominator of 7 to get 3x=147 from there you divide by 3 to get the final answer of x=49

An alternate way to solve it, since 21 is evenly divisible by 3, is to divide each side by 3 first  

37x=21 so you get 17x=7 and then multiplying both sides by 7 to remove the denominator x=49

Answer 2

Let number is X
3/7 of a number is 3x/7
3x/7=12
3x=12×7
3x=84
x=84/3
x=28
The number is 28