Solution :
let the last number be x
we know,
[tex] \boxed{mean = \frac{sum \: \: of \: \: all \: \: observations}{number \: \: of \: \: observations} }[/tex]
So,
[tex] \hookrightarrow \: 8 = \dfrac{22 + x}{4} [/tex]
[tex] \hookrightarrow \: 8 \times 4 = 22 + x[/tex]
[tex] \hookrightarrow \: 32 = 22 + x[/tex]
[tex] \hookrightarrow \: x = 32 - 22[/tex]
[tex] \hookrightarrow \: x = 10[/tex]
therefore, the last number is 10.
