7 is added to a certain number; the sum is multiplied by 5; the product is divided by 9 and 3 is subtracted from the quotient. Thus, if the remainder left is 12, what was the original number?

Question: 7 is added to a certain number; the sum is multiplied by 5; the product is divided by 9 and 3 is subtracted from the quotient. Thus, if the remainder left is 12, what was the original number?

Solution:
let the number be x.

ATQ,
[{5(x + 7)}/9] - 3 = 12
or, 5(x + 7) = 15 × 9
or, x + 7 = 135/5
or, x + 7 = 27
or, x = 27 - 7
∴ x = 20