The way to solve this problem is to turn both denominators into 40
4 * 4 16
_ = --- so Clara will reach 16 people in 40 phone calls
10 * 4 40
3 * 5 15
_ = ---- so Toby will reach 15 people in 40 phone calls
8 * 5 40
Therefore Clara will reach more people in 40 phone calls than Toby.