Question

X+y= -9

x+2y= -25

According to the system of equations above, what is the value of y?

Answer 1

Try this option:
if x+y=-9 is I (one)
and x+2y=-25 is II (two), then
if II-I, then (x+2y)-(x+y)=-25+9 ⇔ y=-16.