Hi! I use the same schooling (WCA) sorry for answering 3 years late
Answer:
x + y = 4 Equation 1
y = 2x -1 Equation 2
-2x + y = -1
x + y = 4
Subtract
I will get
- 3x = -5
Divide by -3
-3x / -3 = - 5 /-3
x = 5/3
Substitute x into equation 1
x + y = 4
x = 5/3
5/3 + y = 4
y = 4 - 5/3
y = 7/3
x = 5/3 y = 7/3