SOLUTION: solve the system of equations using the substitution method. write the solution as an ordered pair. y=3x y-x=18

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Question 250211: solve the system of equations using the substitution method. write the solution as an ordered pair.
y=3x
y-x=18
Answer by tutorcecilia(2152) About Me  (Show Source):
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y=3x
y-x=18
.
y-x=18 [plug in y=3x for the y-term]
(3x)-x=18 [solve for the x-term]
2x=18
2x/2=18/2
x=9
.
y=3x [ plug-in x=9 into either equation and solve for the y-value]
y=3(9)
y=27
.
Check by plugging both x and y-values into either equation:
y-x=18
27-9=18
18=18 [checks out]
.
Solution (9, 27)