Question

The difference of two numbers is 9. The sum of the two numbers is 15. What are the two numbers?

Answer 1

Let numbers be a and b

• a+b=15--(1)
• a-b=9---(2)

Adding both

`\\ \qquad\quad\sf\longmapsto 2a=24`

`\\ \qquad\quad\sf\longmapsto a=(24)/(2)`

`\\ \qquad\quad\sf\longmapsto a=12`

• Put value in eq(2)

`\\ \qquad\quad\sf\longmapsto 12-b=9`

`\\ \qquad\quad\sf\longmapsto b=12-9`

`\\ \qquad\quad\sf\longmapsto b=3`