How do i solve this?

every 3 days seth goes to the gym. brian, his brother, goes every 5 days. what day will they both go to the gym?

a.) the 15th day
b.) the 20th day
c.) the 12th day

Planning for the possibility that your home might get struck by lighting and catch on fire is part of a plan for ?

Arefrigeration system at your company uses temperature sensors fixed to read celsius (°c) values, but the system operators in your control room understand only the fahrenheit scale. you have been asked to make a fahrenheit (°f) label for the high temperature alarm, which is set to ring whenever the system temperature rises above –10°c. what fahrenheit value should you write on the label

Last year, a state university received 3,560 applications from boys. of those applications, 35 percent were from boys who lived in other states. part a)how many applications did the university receive from boys who lived in other states? part b)applications to the university from boys represented 40percent of all applications. how many applications did the university receive in all? i don't how to do part b so me and plz tell how you got your answer