Each week carrie works 40 hours she spend 15% of her time at register

Please, share the goal of the problem.  If Carrie works 40 hours per week and spends 15% of her time at the register, how much time does she NOT spend at the register?  

Subtract 15% from 100%; the result is 85%.  Now find 85% of 40 hours:

0.85(40 hours) = 34 hours.

Please note that I invented part of this problem.  Next time, share all of the info so that someone can help you solve YOUR particular problem.