Question

A number is 4 times another number, If 21 is added to both the numbers then first number becomes (7)/(4) times the other number. What are the numbers?

Answer 1

y = 4x

(y + 21)/(x + 21) = 7/4

(4x + 21)/(x + 21) = 7/4

4(4x + 21) = 7(x + 21)

16x + 84 = 7x + 147

9x = 63, so x = 7 and y = 28.