Find b and c so that (5,b, c) is orthogonal to both (1,2,3) and (1,-2,1)

Anew shopping mall is gaining in popularity. every day since it opened, the number of shoppers is 5% more than the number of shoppers the day before. the total number of shoppers over the first 10 days is 1258 how many shoppers were on the first day?

Acyclist bike x distance at 10 miles per hour .and returns over the same path at 8 miles per hour.what is the cyclist average rate for the round trip in miles per hour ?

What else equals 42 and 30 for multiply