Question

Charles rode 15 miles on his bicycle in 2.5 hours . barb rode her bicycle 8 miles in 1.5 hours at what rate fid Charles ride,in miles per hour with work please

Answer 1

In other words, determine the rate (speed) at which Charles rode his bike.  Barb and her bike are irrelevant here.

The rate / speed is found by dividing "15 miles" by "2.5 hours."  Please do this.