Question 791782
What would be the easiest way to solve this problem ? The only known value is that z=9
*****from this statement and the given equations, one can assume without loss of generality that you meant z is equivalent to Z in this problem and Y is equivalent to y although in mathematics one must be consistent  :-)    *******

we are given
x + Y + Z = 14
x - 2y = -4
Z = 9
substitute for z in equation 1, this gives us two equations in two unknowns
x +y +9 = 14
x -2y = -4
subtract 9 from both sides of =
x +y = 5 and
x = 5 -y
substitute for x in the second equation
5 -y -2y = -4
subtract 5 from both sides of =
-3y = -9
y = 3
x +3 = 5
x = 2
check with second equation
2 -2*3 = -4
-4 = -4
answers check
x = 2, y = 3