3x + y = 5 এবং 5x + 3y = 11 হলে x + y = কত?

প্রশ্ন: 3x + y = 5 এবং 5x + 3y = 11 হলে x + y = কত?

সমাধান: 
3x + y = 5................(1)
5x + 3y = 11............(2)

(1) × 3 - (2) ⇒
9x + 3y - 5x -  3y = 15 - 11
4x = 4
x = 1 

(1) ⇒
3x + y = 5
3 × 1 + y = 5
3 + y = 5
y = 5 - 3
y = 2

x + y = 1 + 2 = 3