Question

he mean of four numbers is 30. If three of the numbers are 12, 50, and 48, what is the fourth number? A. 120 B. 10 C. 12 D. 30

Answer 1

(12+50+48+x)/4=30
12+50+48+x=120
110+x=120
x=120-110
x=10

Answer 2

30 = 12+50+48+a÷4
30×4= 110+a
120=110+a
a=120-110
a =10