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The sum of two numbers is 15 and their difference is 7, What are the two numbers

2 Answers

3 votes
These numbers are 11 and 4

11+4=15
11-4=7
User Anton Schrage
by
7.8k points
6 votes
Greetings!

Let x represent the first number
Let y represent the second number

Create a system of equations, representing the problem:

\left \{ {{x+y=15} \atop {x-y=7}} \right.

Use elimination to solve:

+ \frac{\left \{ {{x+y=15} \atop {x-y=7}} \right. }{2x=22}

Divide both sides by 2.

2x=22

(2x)/(2)= (22)/(2)

x=11

Solve for the other variable:

x+y=15

11+y=15
Add -11 to both sides.

(11+y)+(-11)=(15)+(-11)

y=4

The Solution to this Problem is:

\left[\begin{array}{ccc}x=11,y=4\end{array}\right]

The numbers are 11 and 4.

Hope this helps.
-Benjamin
User FlyingMolga
by
8.3k points

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