Question 939602
___________________rate_____________time_____________distance
Faster_____________r+6_____________t-5/60____________d
OnTime______________r_______________t________________d
Slower_____________r-5____________t+6/60_____________d


Three equations using three unknowns, r, t, d.
Goal is find the value for d.


{{{system((r+6)(t-1/12)=d,rt=d,(r-5)(t+1/10)=d)}}}


{{{system(rt+6t-r/12-1/2=d,rt=d,rt-5t+r/10-1/2=d)}}}


Use the simpler equation to substitute for rt in the Fast and Slow equations, and simplify.  If you handle this correctly then you get a system of two equations in r and t.  Solve that system for r and t...  and you can then evaluate r*t=d.