nilai 60 65 70 75 80 frekuensi 2 6 10 x 4 jika rata-ratanya 71, nilai x adalah...

rata2 =( (60.2)+(65.6)+(70.10)+(75.x)+(80.4))/(2+6+10+x+4)
71 = (120+390+700+75x+320)/(22+x
71(22+x) = 1530 + 75x
1562 + 71 x = 1530 + 75x
1562 - 1530 = 75x - 71x
32 = 4x
x = 32/4
x = 8

60*2)+(65*6)+(70*10)+(75*x)+(80*4)/22+x=71
120+390+700+75x+320=71(22+x)
1530+75x=1568+71x
75x-71x=1562-1530
4x=32
X=32/4
X=8