You can
put this solution on YOUR website!Each change requires a different
equation because a change will make
the graph of

a different
straight line
1st part of trip:

2nd part of trip:

This is 2 equations and 2 unknowns, so
it's solvable
My tip for word problems is: A small amount of time
spent really thinking about what's going on in
general is worth doing a hundred problems.