How fo I substitute

-x+y=-13

3x-y=19

x=3; y = - 10

I will prefer addition of equation instead of substitution, but you asked how to substitute

Step-by-step explanation:

-x+y=-13

y=x-13

3x - (x-13) = 19

3x-x+13=19

2x=6, x=3

-3+y=-13, y=-13+3, y=-10