Barbara spends 1/16 of her time on the phone.How many hours does she have to work in a week so that?

1/16 of her working time Barbara spends on the phone. We are told that this fraction corresponds to 5h/wk. The entirety of her working time per week corresponds to 16/16 = 1. Hence, she works 16 * 5 = 80 hours per week.