Question 791782
Given
(1) z = 9
(2) x + y + z = 14
(3) x - 2y = -4
Substitute z of (1) into (2) and get
(4) x + y + 9 = 14 or
(5) x + y = 5
Now you have two equations, (5) and (3) to solve simultaneously for x and y. Use the following steps;
Subtract equation (3) from equation (5) as follows to get
(6) (x+y) - (x-2y) = 5 - (-4) or
(7) 3y = 9 or
(8) y = 3
Using (2) we get
(9) x = 14 - 9 - 3 or
(10) x = 2
Let's check the values with (1), (2) and (3).
Is (9 = 9)? Yes
Is (2 + 3 + 9 = 14)?
Is (14 = 14)? Yes
Is (2 - 2*3 = -4)?
Is (2 - 6 = -4)?
Is (-4 = -4)? Yes
Answer: {x,y,z} = {2,3,9). The easy way!
PS Don't mix upper case and lower case letters, y and Y, - they are different variables in mathematics and passwords.