Both sides of the equation are the same as *2, so.

3x+4y=2

4y = 2-3 times

y=(2-3x)/4

(2)( 1/4)x+(7/4)y=2

Both sides of the equation are the same as *4, so.

x+7y=8

y=(8-x)/7

5x-3y=x+2y

4x=5y

y=4x/5

(4) 2(3y-3)=6x+4

3y-3=3x+2

3y=3x+5

y=(3x+5)/3

2( 1)y=x+3 ①

7x+5y=9 ②

Substitute ① into ②.

7x+5(x+3)=9

7x+5x+ 15=9

12x=-6

x=- 1/2

Substitute ① y=- 1/2+3=5/2.

∴x=- 1/2； y=5/2

(2) 3s—t=5 ①

5s+2t= 15 ②

By ① formula t=3s-5 ③

③ Substitute into ② formula 5s+2(3s-5)= 15.

5s+6s- 10= 15

s=25/ 1 1

Substitute t = 3 * 25/11-5 = 20/1/in the formula ③.

∴s=25/ 1 1； t=20/ 1 1

(3)3x+4y= 16 ①

5x-6y=33 ②

By ① formula y=( 16-3x)/4 ③

Substitute ③ into ② 5x-6[( 16-3x)/4 ]=33.

5x- 1.5( 16-3x)=33

5x-24+4.5x=33

9.5x=57

x=6

Substitute y = (16-3 * 6)/4 =-1/2 in the formula ③.

∴x=6； y=- 1/2

(4)4〔x-y- 1〕= 3〔 1-y〕2①

x/2+y/3=2 ②

From the equation of formula (2), it is concluded that both sides are equal to *6.

3x+2y= 12

x=( 12-2y)/3 ③

Replace Type ③ with Type ①.

4[( 12-2y)/3-y- 1]= 3( 1-y)-2

Both sides of the equation are the same as *3.

4( 12-2y)- 12y- 12 = 9-9y-6

48-8y- 12y- 12=3-9y

36-20 = 3-9 years old

1 1y=33

y=3

Substitute in ③ formula, X=( 12-2y)/3.

x=( 12-2*3)/3=2

∴x=2； y=3