Question 835581
______________speed__________time__________distance
passenger_____r+18___________t-1.5_________d
freight________r______________t____________d


t = unknown, but quickly solvable.
r = unknown
{{{t-1.5=2.5}}} hours, according to description.
{{{t=2.5+1.5=highlight_green(4)}}} hours, so t is now known.


Revise data table:

______________speed__________time__________distance___Equations
passenger_____r+18___________4-1.5=2.5_________d______{{{(r+18)*2.5=d}}}
freight________r______________4____________d__________{{{r*4=d}}}


Two different expressions for d are equal.
{{{highlight((r+18)*2.5=4*r)}}} Solve for r.