You have a system of equations in two unknowns, x and y.
2x - 3y = -1
y = x - 1
There are several methods for solving systems of equations, but since your second equation is already solved for y, I will use the substitution method since in that method, the first step is to solve an equation for one variable.
The second equation tells us that y is the same as x - 1.
Where you see y in the first equation, substitute it with x - 1.
Here is the first equation with the y in bold face.
2x - 3y = -1
Now we do the substitution step.
We rewrite the first equation, but we write x - 1 instead of y. We are substituting x - 1 for y.
2x - 3(x - 1) = -1
As you can see, y was substituted by x - 1. The parentheses are needed to show we need to multiply 3 by x - 1 and not just be x.
Now we have a single equation is a single unknown, so we can solve for x.
2x - 3(x - 1) = -1
Distribute the -3.
2x - 3x + 3 = -1
Add like terms on the left side.
-x + 3 = -1
Subtract 3 from both sides.
-x = -4
Divide both sides by -1.
x = 4
Now that we know x, we substitute x into either of the original equations to find y. Since the second original equation is already solved for y, I will use the second original equation.
y = x - 1
y = 4 - 1
y = 3
Solution: x = 4 and y = 3