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

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

$\\ \qquad\quad\sf\longmapsto a=\dfrac{24}{2}$

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

• Put value in eq(2)

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

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

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