5 is added to a certain number; the sum is multiplied by 7; the product is divided by 6 and 9 is subtracted from the quotient. Thus, if the remainder left is 12, what was the original number?

Question: 5 is added to a certain number; the sum is multiplied by 7; the product is divided by 6 and 9 is subtracted from the quotient. Thus, if the remainder left is 12, what was the original number?

Solution:
let the number be x.

ATQ,
[{7(x + 5)}/6] - 9 = 12
⇒ {7(x + 5)}/6 = 12 + 9
⇒ 7(x + 5) = 21 × 6
⇒ x + 5 = 126/7
⇒ x + 5 = 18
⇒ x = 18 - 5
∴ x = 13