Solution
= Solution
Because $X$ takes values only in $[0,1]$, its <cumulative distribution function> must satisfy $F(1)=1$. Thus
$$
1=A\left(\frac13-\frac14\right)=\frac A{12},\qquad\boxed{A=12}.
$$
= Solution
Because $X$ takes values only in $[0,1]$, its <cumulative distribution function> must satisfy $F(1)=1$. Thus
$$
1=A\left(\frac13-\frac14\right)=\frac A{12},\qquad\boxed{A=12}.
$$