x+y=-14 subtract y from both sides x=-14-y subsitute for x in second equation (-14-y)y=-240 multiply -y^2-14y=-240 add y^2+14y to both sides 0=y^2+14y-240 use quadratic equation to solve which is if you have ax^2+bx+c so
a=1 b=14 c=-240 subsitute and get (+/- means that there are 2 equations exg 2+/-8=2+8 and 2-8)