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If x + y = 7 and 2x - y = 2, then y - ?

User Hcarreras
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2 Answers

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First you isolate the variable, then you substitute it to the other problem. I did it for you, x=3 and y=4
If x + y = 7 and 2x - y = 2, then y - ?-example-1
User Svilen
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5.4k points
5 votes

Answer:

(3,4)

Explanation:

This system is already setup for linear combination/elimination (don't know what your class calls it).

The reason I say this is because if you add the equations together the variable y will be eliminated giving you a chance to solve for x.

Let's do that:

x+y=7

2x-y=2

--------------Add.

3x =9

Divide both sides by 3:

x =3

Using one of the equations (doesn't matter; you choose) along with x=3 we can find y.

I choose x+y=7 with x=3.

x+y=7 with x=3:

3+y=7

Subtract 3 on both sides:

y=7-3

Simplify:

y=4

The solution is (x,y)=(3,4).

Let's check our solution by plugging it in:

x+y=7

3+4=7

7=7 is true.

2x-y=2

2(3)-4=2

6-4=2

2=2 is true.

Since both equations are true for (x,y)=(3,4), then (3,4) is definitely a solution.

So we have solution confirmation.

User Trimax
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