Answer
$16.2\; miles$.
Work Step by Step
The given equation for the total distance walking and traveling by bus is
$=0.06t+0.5(50-t)$
(a.) Use distributive property.
$=0.06t+0.5\times 50-0.5\times t$
$=25-0.5\times t+0.06 t$
Use distributive property.
$=25+(-0.5+0.06) t$
Simplify.
$=25+(-0.44) t$
$=25-0.44 t$
(b.) From the question we have
$t=20$ minutes.
Substitute the value of $t$ into the resultant from part (a.).
$=25-0.44 (20)$
Clear the parentheses.
$=25-8.8$
Simplify.
$=16.2\; miles$.
