by elimination you can subtract the two equations
x - 2y = -29
-(x - y = -11) the x's will subtract to be 0 and you'll get -2y + y = -29 + 11
or -y = -18
then y = 18
substitute this in for y in either equation
x - 2(18) = -29
x-36 = -29 add 36 to both sides and x=7
answer is (7, 18)