Question

The mean of 4 ,9,10 and x is 8. Find x

Answer 1

4+9+10+X÷4=8

23+X=32

X=32-23

X=9

Answer 2

Answer:

$mean \: = \frac{sum \: of \: observations}{number \: of \: observations}$

$\frac{4 + 9 + 10 + x}{4} = 8$

$\frac{23 + x}{4} = 8$

$23 + x \: = 8 \times 4$

$23 + x \: = 32$

$x \: = 32 - 23$

$x \: = 9$

I hope this answers your question !