The mean score for a set of three numbers is 7 find the new mean when a score of 21 is added

Answer 1

(x+y+z)/3 = 7

x+y+z = 21

(x+y+z+21)/4 =

((x+y+z)+21)/4 =

(21 + 21)/4 =

42/4 =

21/2 =

10.5