Answer:
a=9 b=18
Step by-step explanation:
First we will find b.
Because there is no 18 in this set and it's an even set of numbers, this would mean that 18 is not present in the set.
The only way for 18 to the be the mean is for b to equal 19. When calculating the average of 17 and 19 your average, or mean, is 18.
a has to be a number ranging from 7-12.
Through trial and error, it can be found that the missing value of a is 9.
Hope this helps!
-MoCKEry