Answer
$225\;mi$.
Work Step by Step
Given values are
Distance $d_1=90.0\;mi$.
Time $t_1=1\frac{1}{2}\;h$.
Let the speed is
$s=\frac{d}{t}$
Substitute all the values.
$s=\frac{90.0\;mi}{1\frac{1}{2}\;h}$
Distance $d_2$.
Time $t_2=3\frac{3}{4}\;h$.
Speed is same.
$s=\frac{d_1}{t_1}=\frac{d_2}{t_2}$
Substitute all the values.
$\Rightarrow \frac{90.0\;mi}{1\frac{1}{2}\;h}=\frac{d_2}{3\frac{3}{4}\;h}$
Simplify.
$\Rightarrow \frac{90.0\;mi}{\frac{3}{2}\;h}=\frac{d_2}{\frac{15}{4}\;h}$
$\Rightarrow 225\;mi=d_2$.
