2.∫2x-y = 5∴y = 2x-5 generation 7x-3y = 20 to get 7x-3x (2x-5) = 20 ∴ x = 5 y = 5.

3，y = 2x+4x-y = 1，4x-(2x+3) = 1 ∴ 2x = 4 ∴ x = 2y = 7。

4.∫5x+y = 2∴y = 2-5x generation x-3y = 4 and x-3x (2-5x) = 4 ∴16x =10.

∴x=5/8 y=﹣9/8

5、3x-2y = 1……( 1)2x+3y=﹣7……(2)

(1) × 3+(2 )× 2:13x = ﹣1∴ x = ﹣113rd generation.

﹣33/ 13-2y= 1 ∴2y=﹣33/ 13- 1 ∴2y=﹣46/ 1 1 ∴y=﹣23/ 13