make x the subject of x-7=v
3x-1=4-2x
2x+5=3x-2
2x+3x-2
3x-y=4
-9x+3y=-12
P=I2xR1 despejar R1
9x+40=4x+5
x+3=2x
x+2y=2
7x-3y=-20
x+3=2x-6
