Question 90578
You can use the formula:{{{d = rt}}} where d = distance, r = rate(speed) and t = time of travel.
For the outbound trip: {{{t[1] = 5}}} hrs, so you can write:
{{{d[1] = 5r[1]}}}
For the return trip, the rate was 5 mph faster than for the outbound trip, so {{{r[2] = (r[1]+5)}}} and {{{t[2] = 4}}}, so you can write:
{{{d[2] = 4(r[1]+5)}}}
But the distance out is the same as the distance back, so...
{{{d[1] = d[2]}}} or...
{{{5r[1] = 4(r[1]+5)}}} Simplify and solve for {{{r[1]}}}
{{{5r[1] = 4r[1]+20}}}
{{{r[1] = 20}}}mph This is the outbound speed.
{{{r[2] = r[1]+5}}}
{{{r[2] = 25}}}mph  This is the return speed.