What is the rule of add 15,subtract 10

During your cycling trip, you and your friends often stayed in hostels. the prices of these are listed below. hostel standard room (price per night) with breakfast (price per night) super sleep hostels £22.45 £28.65 normandy nights £18.55 £25 zzzola hostels £24.50 £30.99 belgian beds £11.20 £18.55 night-time rest days ? £33 what is the range in cost for a single night, including both standard room prices and with breakfast prices?

According to the general equation for conditional probability if p(anb)=3/7 and p(b)=7/8 what is p(a i b)

Simplify this expression. 8x 16(x + y)