Hi! I'll try to help
It gives you two equations, one for "x" and one for "y"
All you have to do is replace the variable "y" with its value in the second equation. Might be kind of confusing so let's do one.
y=4x
3x-y=1
Since we know that "y" is the same as 4x, you can rewrite the equation as
3x-4x=1
Next, all you have to do is combine like terms as solve "3x-4x" which is -x
Let's rewrite the equation, then:
-x=1
You can simplify it to
x=-1
by dividing both sides by negative one, in other words swapping the negative sign so that "x" is positive