The mean of seven numbers is 21. Five of the numbers are 18, 23, 21, 17, and 19. One of the remaining numbers is 3/4 of the other remaining number. Find the two unknown numbers.

16 you are so welcom

Mean of a set of numbers is

(sum of the values of the numbers in the set) / (how many numbers in the set) = mean

example

1,2,4

mean is

(1+2+4) / 3=7/3

ok

mean of 7 numbers is 21

(7numbers) / 7=21

"5 of them are 18,23,21,17"

(mentally do 7-5=2)

2 missing

"one of the remaining is 3/4 of other"

the 2 remaining is x and 3/4x

nmow we have

(18+23+21+17+19+x+3/4x) / 7=21

add like terms

(98+1 and 3/4x) / 7=21

mulitply everybody by 7

98+7/4x=147

minus 98 both sides

7/4x=49

multiply both sides by 4/7 to clear fraction (7/4 times 4/7=28/28=1, so 1x=x)

1x=196/7

x=28

the other number is 3/4 of this

3/4x=3/4*28=21

the 2 unknowns are 28 arnd 21