#color(red)("To find x and y, you need to solve these equations simultaneously:")#

#y=-2x-17# #.........(1)#

#-x+11y=66# #.........(2)#

sub #(1)# into #(2)#:

#-x+11(-2x-17)=66#

#color(red)("Expand the brackets:")#

#-x-22x-187=66#

#color(red)("Group like terms:")#

#-23x-187=66#

#color(red)("Put all integers on the right:")#

#-23x=253#

#color(red)("Isolate x:")#

#therefore x=-11#

#color(red)("Now to find y:")#

sub #x=-11# into #(1)#:

#y=-2(-11)-17#

#color(red)("Expand brackets and simplify:")#

#y=22-17#

#therefore y=5#

#color(red)("Putting what we have found all together:")#

#therefore x=-11,# #y=5#