#5x+y=-7" "color(red)(5x)=color(green)(-7-y)" "(1)#
#5x-9y=-23" "color(red)(5x)=color(green)(-23+9y)#
#if color(red)(5x=5x) " then "color(green)(-7-y=-23+9y)#
#-7+23=9y+y#
#16=10y#
#y=1,6#
#"use equation (1)"#
#5x=-7-1,6#
#5x=-8,6#
#x=-(8,6)/5#
#x=-1,72#