Solve the following system of equations: 7x - y = 4 and 3x + 2y = 9

Use substitution method

7x - y = 4 eqn 1

3x + 2y = 9 eqn 2

rearrange eqn 1:

y = 7x - 4

sub it in eqn 2

3x + 2 (7x-4) = 9

solve for x:

3x + 14x - 8 = 9

17x = 9+8

x = 1

sub x=1 in eqn 1

y = 7 (1) - 4

y = 3

solution is (1, 3)

{7x-y=4 / * 2

{3x+2y=9

{14x-2y=8

{3x+2y=9 (+)

14x+3x-2y+2y=8+9

17x=17 / : 17

x=1

7x-y=4

7*1-y=4

-y=-3

y=3

Solution: (1; 3)