4) Which linear system has been correctly solved for one of the variables from the following system?
2x - y = -1
2x + y = -7

A. 2x - y = -1 y = 2x - 7
B. 2x - y = -1 y = -2x + 7
C .y = 2x + 1 2x + y = -7
D. y = -2x + 7 2x + y = -7