[tex]X[/tex] has PDF
[tex]f_X(x)=\begin{cases}\frac1{10}&\text{for }0\le x\le10\\0&\text{otherwise}\end{cases}[/tex]
and thus CDF
[tex]F_X(x)=\begin{cases}0&\text{for }x<0\\\frac x{10}&\text{for }0\le x\le10\\1&\text{for }x>10\end{cases}[/tex]
Because [tex]X[/tex] is continuous, we have
[tex]P(X<1\text{ or }X>8)=1-P(1\le X\le8)=1-(P(X\le8)-P(X\le1))[/tex]
[tex]P(X<1\text{ or }X>8)=1-P(X\le 8)+P(X\le1)[/tex]
[tex]P(X<1\text{ or }X>8)=1-F_X(8)+F_X(1)[/tex]
[tex]P(X<1\text{ or }X>8)=1-\dfrac8{10}+\dfrac1{10}=\boxed{\dfrac3{10}}[/tex]
