math
posted by karly on .
Solve using elimination method 7x+5y=56;21x2y=168

thsi is how i would do it
lets say equation 1 will be 7x + 5y = 56
and equation 2 is 21x  2y = 168
nothign can cancel out if you llok at the equation so what i would do is multiply equation 1 by a negative 3 that way the 7x becomes a positive 21x to cancel out(but you have to multpliy everything in the equation by 3 not just the 7x)
so you will have;
21x 15y = 168
now add the two equation together
(21x  15y= 168) + (21x  2y=168)
notice the x and the total on the right side of equal sign cancels leaving you with :
17y=o y=0 since 0 dvide by anything is still zero now choose any of your original equation and plug in 0 for y and solve for x