.
Let "r" be the rate of the first cyclist, in mph.
Then the rate of the second cyclist is (r-10) mph.
The condition says:
= 2.4.
It is your "time equation" to solve for r.
To solve it, multiply oth sides by r*(r-10). You will get
210r - 210(r-10) = 2.4r*(r-10).
Simplify and solve this quadratic equation for "r". It is just arithmetic.
Good luck !
If you are interested in learning Travel and Distance problems, there are a lot of solved problems for you in this site.
You can find them in this free of charge online textbook on ALGEBRA-I in this site
ALGEBRA-I - YOUR ONLINE TEXTBOOK.
The Travel and Distance problems are the part of this textbook under the section "Word problems", the topic "Travel and Distance problems".