This is the best scenario you could hope for in a system of equations, because two of the variables are already additive inverses. #(+y) +(-y) =0#
We simply need to add the two equations together and the #y#-terms will be eliminated
#color(white)(..................)2x+y = 0#..............................A
#color(white)(..................)ul(5x-y = 7)#..............................B
#A+B: " "7x" "=7#
#color(white)(...................)x" " = 1#
Now that we know the value of #x#, plug it into #A or B# to find #y#
#color(white)(..................)2(1)+y = 0#..............................A
#color(white)(............................)y = -2#
