9. 2x - 3y = 21

y=3-x

Answer: (6,-3)

Explanation:

(1) 2 x-3y=21

(2) y = 3 - x

Substituting eq 2 in eq 1

2 x - 3 (3-x) = 21

2 x-9+3x=21

5 x - 9 = 21

5 x = 30

x = 6

Put x = 6 in eq 2 we get,

y = 3 - 6

y = - 3

Solution : (6, - 3)