Answer:
The number is 7.
Explanation:
In this case we have an unkown variable that is a number. We will call this number by "x", this is what we want to calculate. In the first part it is said that the number or x is added to the numerator and in the second part it is said that twice the number is added to the denominator, and that this fraction is equal to 1/3. So we have:
1/3 = (12 + x)/(43 + 2*x)
43 + 2*x = 3*(12 + x)
43 + 2*x = 36 + 3*x
43 - 36 = 3*x - 2*x
x = 7
The number is 7.