Expert: Ahmed Salami - 10/29/2008

Question
so yea i'm trying to find 3 numbers that works in all 3 equations so yea here you go                    x+2y=12
                                              3y-4z=25
                                              x+6y+z=20 now you have to find x y and z

Answer
Hi Ashley,
x + 2y = 12
3y - 4z = 25
x + 6y + z = 20
From the first equation,
x = 12 - 2y
From the second equation,
4z = 3y - 25
z = (3y - 25)/4
Inserting into the third equation,
x + 6y + z = 20   becomes
(12 - 2y) + 6y + (3y - 25)/4 = 20
multiplying through by 4,
4(12 - 2y) + 4(6y) + (3y - 25) = 4(20)
48 - 8y + 24y + 3y - 25 = 80
19y = 57
y = 3
So,
x = 12 - 2(3)
 = 12 - 6
 = 6
and
z = (3(3) - 25)/4
 = (9 - 25)/4
 = -16/4
 = -4

Regards