Let 9(1-x) = 27y be equation one and let x-y = -11/2 be equation two
Simplify -11/2 into -5.5 and make x the subject in equation two by moving y to the other side as a positive value. So now you have x= -5.5+y (now let that be equation two)
Sub equation two into equation one so that you get 9(1-(-5.5+y)= 27y
Expand brackets 9(1+5.5-y)= 27y
Simplify brackets 9(6.5-y)= 27y
Expand brackets 58.5-9y= 27y
Take -9y to the other side as a positive number
58.5= -36y
Divide both sides by -36
y= 1.625
For x, substitute the value of y into equation two
x= -5.5+1.625
x= -3.875
To finally answer the question aadd the value of x and y together
