If you’re trying to find the intersection between these two functions you need a system with curly brackets.
y = -1
y = (-5/2)x + 4
You already know the y coordinates of the intersection. Now just substitute the y in the second function with -1.
-1 = (-5/2)x + 4
<=> 5 = (5/2)x
<=> (2/5)5 = x
<=> x = 2
The intersection is (2, -1)
