Question 1042836
RT=D is the travel rates rule relating "speed" R, time T, and distance D.


{{{system(80*t=280,(80-10)(t+x)=280)}}}
two unknown variables, two equations;
You can simply solve for t right away... and then......




Forming a table of data can often help to find the equations to make for the problem description.  Here, the description was taken directly to the two listed equations without a data table.