How do you solve the system of equations #x= - 4# and #- 8x - 5y = - 18# by using substitution?

1 Answer
Adam L.
Mar 14, 2017

Y is equal to 10. For how, see the explanation.

Explanation:

Substitute #x# with #-4# in the second equation.
This gets you:
#-8(-4) - 5y = -18#
Multiply #-8# and #-4#:
#32 - 5y = -18#
Subtract 32 from both sides:
#-5y = -50#
Divide both sides by negative five:
#y = 10#
You don't need to find x, since it's already given.
There are other ways to solve this with substitution, involving adding or subtracting different things in a different order, but they all end up with the same answer.

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