Question

A first number plus twice the second number is 7. Twice the first number plus the second totals 20. Find the number

Answer 1

x+y=7
2x+y=20

y=7-x

Now substitute

2x+7-x=20
x+7=20
x=20-7
x=13

Which means y=-6 if you put it into the first 2 equations

Answer 2

As per the problem

A first number plus twice the second number is 7

Twice the first number plus the second totals 20

Let the first number is x and second number is y then we can write

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