Question

One number is 9 more than another number. The sum of the numbers is 25. What is one of the numbers?A) 9B) 8C) 16D) 17

Answer 1

B) 8 or D) 17

Explanation

Let's call x to one unknown number and y to the other number.

If one number is 9 more than another number, then:

`y=x+9\text{ \lparen eq. 1\rparen}`

Given that the sum of the numbers is 25, then:

`x+y=25\text{ \lparen eq. 2\rparen}`

Substituting equation 1 into equation 2 and solving for x:

`\begin{gathered} x+x+9=25 \\ 2x+9=25 \\ 2x+9-9=25-9 \\ 2x=16 \\ (2x)/(2)=(16)/(2) \\ x=8 \end{gathered}`

Substituting x = 8 into the first equation:

`\begin{gathered} y=8+9 \\ y=17 \end{gathered}`

Then, one of the numbers is 8 and the other one is 17