Alright, lets get started.
Suppose first bicyclist speed is = x mph
As given in question, second one is 4 mph slower than first, hence
Speed of second bicyclist is = (x-4) mph
They both travels 3 hrs so,
distance covered by first bicyclist :
![distance = speed* time](https://img.qammunity.org/2019/formulas/mathematics/college/o9tatuedx6x0c6akjf286jg6rgzcvxlz3h.png)
![d1 = 3x](https://img.qammunity.org/2019/formulas/mathematics/college/bekc8yk19tvfydas1ux3l40fq32xz1eodh.png)
distance covered by second bicyclist :
![d2= 3 (x-4)](https://img.qammunity.org/2019/formulas/mathematics/college/97k76vz9p07l2hgssowfyrfo5tntcdl2c1.png)
4 miles were still left after 3 hrs of driving.
It means they covered 88 - 4 = 84 miles together
![d1 + d2 = 84](https://img.qammunity.org/2019/formulas/mathematics/college/oa31acoerp0baze40rso79z0v2p4q109ls.png)
![3x + 3 (x-4) = 84](https://img.qammunity.org/2019/formulas/mathematics/college/e7tu6xwwo5jsdybugyolw88xihinc348wn.png)
![3x + 3x - 12 = 84](https://img.qammunity.org/2019/formulas/mathematics/college/rbv53y5r9zaklkbu9koukb34toxhwb3818.png)
Adding 12 in both sides
![6x - 12 + 12 = 84 + 12](https://img.qammunity.org/2019/formulas/mathematics/college/5m4br2jmqze1h7orio7qrkl607gx46ywm0.png)
![6x = 96](https://img.qammunity.org/2019/formulas/mathematics/college/34uvpb84xcr0gs3fkc0hvjln53vcing6i1.png)
Dividing 6 in both sides
![(6x)/(6)= (96)/(6)](https://img.qammunity.org/2019/formulas/mathematics/college/w51x5j7vkwl4h4nxgkqq462wy30l0o9fmp.png)
![x = 16](https://img.qammunity.org/2019/formulas/mathematics/college/f8masn3utcvaqcp9hf4lalr53x1tkiq7bl.png)
Means speed of first bicyclist = 16 mph
Speed of second bicyclist =
mph
Hence speed of both bicyclist are 16 mph and 12 mph. : Answer
Hope it will help :)