-- Posted by ashleexoxo at 8:16 pm on Jan. 5, 2009 well i do know you have to plug in numbers but can somehelp me??? im trying to get help on all the problems i dont know solve each system by substitution 1.   x - y +2z = 7      2x + y + z = 8      x         -z  = 5 2.   5x - y + z = 4       x +2y - z = 5     2x + 3y -3z = 5 -- Posted by boombabyboom at 8:17 pm on Jan. 5, 2009 1. 0 2.4 -- Posted by bakaninja at 8:17 pm on Jan. 5, 2009 huh??? -- Posted by noraa at 8:18 pm on Jan. 5, 2009 that's really easy. However I don't feel like working them because i have my own damn math that's not for the sixth grade. -- Posted by XTCofGOLD at 8:18 pm on Jan. 5, 2009 x-z=5 so x=5+z so Everytime you see an X, substitute (5+z) in place of the x. -- Posted by PreppyPeyton at 8:18 pm on Jan. 5, 2009 Thats some 7th grade ish, well for me. I will not help you with your homework, nah I dont have any paper and dont feel like doing the head thing. -- Posted by matto at 8:19 pm on Jan. 5, 2009 use descriminants instead!  so much faster. -- Posted by ivy1994 at 8:20 pm on Jan. 5, 2009 The first one is 0 the second is 4 -- Posted by noraa at 8:20 pm on Jan. 5, 2009 Quote: from XTCofGOLD at 8:18 pm on Jan. 5, 2009 x-z=5 so x=5+z so Everytime you see an X, substitute (5+z) in place of the x. nooo. x=blank z=-5 -- Posted by HuffleHaire at 8:26 pm on Jan. 5, 2009 Quote: from XTCofGOLD at 10:18 pm on Jan. 5, 2009 x-z=5 so x=5+z so Everytime you see an X, substitute (5+z) in place of the x. And then combine the two resulting equations to get your final variable