Question 269831
This is an RTD problem. Here is a table based on the given information
trains . . . . . . . . .rate . . . . . . . . .time . . . . . . . . .distance
freight. . . . . . . . r - 30 . . . . . . . . .3 . . . . . . . . . . 3r - 90
express. . . . . . . .r . . . . . . . . . . .  . 3 . . . . . . . . . . . 3r
totals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .390
Look at the last column, we get
{{{3r - 90 + 3r = 390}}}
simplify to get
{{{6r - 90 = 380}}}
add 90 to get
{{{6r = 480}}}
divide to get
express: {{{r = 80}}}
freight: {{{r-30 = 50}}}