2s-t=5

1 formula -2 formula ×2, get

3t+2t=5- 10

t=- 1

1 formula +2 formula ×3, get

4s+6s=5+ 15

s=2

(2)5X-6y=9

7x-4y=-5

1 formula ×2-2 formula ×3, get

10x-2 1x = 18+ 15

x=-3

1 formula ×7-2 formula ×5, get

-42y+20y=63+25

y=-4

(3)4x-3y= 14

5x+3y=3 1

1 type +2 type, obtained

4x+5x= 14+3 1

x=5

1 formula× 5-2 formula× 4, get

- 15y- 12y = 70- 124

y=2

(4) 3(x- 1)=y+5

5(y- 1)=3(x+5)

The transformation of formula 1 is 3x-3 = y+5 = ×-y = 8.

The variation of Formula 2 is: 5y-5 = 3x+15 = "3x-5y =-20.

Type 3+type 4, get

-y-5y=8-20

y=2

3 ×5-4, get

15x-3x=40+20

x=5