Mean=total/the number of values =>total=mean*the number of values
the total of the first set of 8 numbers is : total=8*8=64
the total of the second set of 12 numbers is: 12m
the total of the 20 numbers is: 64+12m
the mean of the 20 number is: (64+12m)/20=5
solve for m: 64+12m=100
12m=36
m=3
Answer:
Twenty decreased by a number. The question says that "a number" =X.
twenty = 20
decreased = minus
by a number = X
Put this all in a line and you get...
an answer of:
20 - X.
