Question

The average of 3, 15, and my number is 40. What is my number?

I'll give 30 points!

Answer 1

102

Explanation:

The average is calculated using

average =
`(totalscore)/(count)`

let your score be x, then

`(3+15+x)/(3)` = 40 ( multiply both sides by 4 )

18 + x = 120 ( subtract 18 from both sides )

x = 102 ← your number