My Math Forum Linear equation in three variables

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 September 20th, 2011, 05:56 AM #1 Newbie   Joined: Sep 2011 Posts: 9 Thanks: 0 Linear equation in three variables What is the value of “y” in the following system of equations? x + y + z = 75 ; -2x + y – z = -15 a. 0 b. 5 c. 15 d. 60
 September 20th, 2011, 08:10 AM #2 Global Moderator   Joined: Dec 2006 Posts: 20,469 Thanks: 2038 Is something mistyped or omitted? The equations imply that y = 30 + x/2 = 45 - z/3.
September 20th, 2011, 12:42 PM   #3
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Re: Linear equation in three variables

Quote:
 Originally Posted by Qwertyqwerty What is the value of “y” in the following system of equations? x + y + z = 75 ; -2x + y – z = -15 a. 0 b. 5 c. 15 d. 60
You have 3 unknowns - you need 3 equations.

 September 20th, 2011, 03:31 PM #4 Global Moderator   Joined: Dec 2006 Posts: 20,469 Thanks: 2038 With only the two equations, y can't be calculated, but you can calculate 3x + 2z.
 September 20th, 2011, 10:38 PM #5 Newbie   Joined: Sep 2011 Posts: 9 Thanks: 0 Re: Linear equation in three variables This is it, word for word. Thanks anyway.

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