Answer:
x = 15/2 (15 over 2)
y = 8
Explanation:
there 3 different way to do this (substitution, Elimination and Matrix)
ill be showing substitution ( you use the answer of one of the variables and substitute it for the other questions variable)
4 + y = 12
y = 12 -4
y = 8
y = -2x - 7
8 = 2x - 7
8 + 7 = 2x
15 = 2x
x = 15/2
hope this helped and made a little sense!