Question

The average of 3 numbers is 7. two of the numbers are 8 and 9. what is the third?

Answer 1

Make an equation. x will be the third number.

To find the average, you add up the numbers then divide the sum by the number of numbers you added up.

(8 + 9 + x) ÷ 3 = 7
Now solve. Add up like terms (8 + 9).

(17 + x) ÷ 3 = 7
Multiply both sides by 3.

17 + x = 21
Subtract both sides by 17.

x = 4

The third number is 4.

Answer 2

(8+9+x)/3=7
(17+x)=21
x=4