Let 5x be the number of stamps Michael had originally. Then Tom had 4x stamps originally. After Michael gave away 3/7 of his stamps, you have THIS equation= 4x - 40. To solve, multiply both sides by 7. You will get 20x = 28x - 280 280 = 28x - 20x 280 = 8x x = 280/8 = 35. Tom had 4x = 4*35 = 140 stamps originally. ANSWER
Let number Tom had, be T
Then Michael had:
If Michael gave away, then he had: remaining
We then get:
5T = 7T - 280 ------ Multiplying by LCD, 7
5T - 7T = - 280
- 2T = - 280
Original number Tom had. or