Question

the average of a set of 10 numbers is 6. nine of the numbers are as follows: 3,4,5,6,7,10,1,3,12. what's the tenth number?

Answer 1

3+4+5+6+7+10+1+3+12 + x = 10*6 = 60
51 + x = 60

x = 60-51 = 9

Answer = 9