If 12x + 13y = 29 and 13x + 12y = 21, find x + y.

Ans. 12x + 13y = 29 and 13x + 12y = 21 [Given]

Adding the given equations

12x + 13y = 29 13x + 12y = 21 25x + 25y = 50

∴ 25(x + y ) = 50

∴ x + y = 50/25

∴ x + y = 2