How do you solve the system #a + 2b = -2#, #-a + b + 4c = -7#, #2a + 3b -c =5#?
I'm going to use the first equation to substitute for a in the other two equations:
And we can now use this last equation to substitute into the one prior:
And now let's find b:
And check it:
And now let's find the last variable:
and check it: