mean is (sum of the values of the numbers in the set)/(how many numbers are in the set)
first bit
mean of 12 numbers is 5.5 is the same as
(12 numbers)/12=5.5
the second bit
mean of 8 numbers is k
(8 numbers)/8=k
(12numbres+8numbers)/20=8.5
interesting
one way is to solve the first and second equations for 12numbers and 8numbers
(12numbers)/12=5.5
times 12 both sides
12numbers=66
(8numbers)/8=k
multiply 8 both sides
8numbers=8k
input
(66+8k)/20=8.5
mulitply both sides by 20
66+8k=170
minus 66 both sides
8k=104
divide 8 both sides
k=13
k=13
