Answer:
x=1, y=-2
Explanation:
According to the substitution property, if x = y, then x can be substituted for y in any equation, and y can be substituted for x in any equation.
We are already given the values:
y=x-3
y+3x=1
We can substitute y into the equation.
As so-

Combine common terms:

Now solve for x. To solve for a variable, we must isolate it:
Add 3 to both sides:

The last thing, 4 is being multiplied to x, so we must divide it to both sides to isolate the variable.

Now we can just substitute the x value into the y equation:

It is always better to check our answers, we can substitute our x and y into the equation:

We are right! :)) Hope it helps!
x=1, y=-2
(1,-2)