Question 1190990
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Let's solve the first equation for x
x - 7y = -11
x = -11 + 7y


We'll then plug this into the other equation.
Wherever you see an x, replace it with (-11+7y)
The term "substitute" effectively means "replace".
So,
5x + 2y = -18
5(-11+7y) + 2y = -18
-55+35y + 2y = -18
-55+37y = -18
37y = -18+55
37y = 37
y = 37/37
y = 1


We can now find x based on that
x = -11+7y
x = -11+7(1)
x = -11+7
x = -4


<font color=red>Solution: x = -4 and y = 1</font>


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Check:


Plug x = -4 and y = 1 into the first original equation
x-7y = -11
-4-7(1) = -11
-4-7 = -11
-11 = -11


Repeat for the other original equation as well
5x + 2y = -18
5(-4) + 2(1) = -18
-20 + 2 = -18
-18 = -18
For each equation above, we get a true statement (i.e. the same number on both sides).
The solution is fully confirmed.
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