Answer :
We have:
X + 2Y = 11
X = -1 + 2Y
=> X + 2Y = 11 <=> -1 + 2Y + 2Y = 11
=> 4Y = 12
=> Y = 3
=> X = -1+2x3 = 5
X + 2Y = 11
X = -1 + 2Y
=> X + 2Y = 11 <=> -1 + 2Y + 2Y = 11
=> 4Y = 12
=> Y = 3
=> X = -1+2x3 = 5