Thread: solve please

using the substitution method

5x +7y = -1
-6x + y = 20

What are you having trouble with, just eliminate one of the variables and solve for the other.

Originally Posted by mathdummy22

using the substitution method

5x +7y = -1
-6x + y = 20

Solve the second equation for y.



Substitute 6x+20 for y in the first equation and solve for x.

Once you have x, you can use either equation to find y.

i get x = -139/47 and y= 106/47..... I have no clue what Im doing wrong

5x +7y = -1
-6x + y = 20

y = 6x+20
7y = 42x +140
5x+42X+140 =-1 Here is where you screw up.
47x = -141
x = -3
y = 2 by substitution.

Solve the second equation for y.



Substitute back into 1st equation:









Now solve for y using

Originally Posted by terr13

5x+42X+140 =-1 Here is where you screw up.

When I screw something up, I always try to screw it back down.