# The average of 63 and one other number is 33. What's the other number?

3

#### Explanation:

The average of two numbers is the sum of the two numbers, divided by 2. Like this:

$\frac{{x}_{1} + {x}_{2}}{2} = a v g$

We are given ${x}_{1} , a v g$ and are asked to find ${x}_{2}$:

$\frac{63 + {x}_{2}}{2} = 33$

$\left(63 + {x}_{2}\right) = 66$

${x}_{2} = 3$