2x+3y=12
3x-y=7
use subsituttion
make one of the equations equal to a placeholder
3x-y=7
subtract 7
3x-7-y=0
add y
3x-7=y
subsisute 3x-7 for y in first equation
2x+3(3x-7)=12
2x+9x-21=12
11x-21=12
add 21 to both sides
11x=33
divide both sides by 11
x=3
subsitute x for 3 in any equation
3x-7=y
3(3)-7=y
9-7=
2=y
x=3
y=2