Answer:
45
Step-by-step explanation: first we want to find out the time it takes to do one full lap of skiing. in order to do this you have to add 4 to 5. we do this because if we start at the bottom of the hill we have to ride 4 min up to the top then 5 min to get back to the bottom. so in all it will 9 min to do one full lap. because we want to find out how long it will take to do 5 laps we do 9x5=45