How do i get the common denominator for the whole number from 6 - 3½

Tan198=asin164=? how to solve this? ?

Yvaries directly as x. y =90 when x=6. find y when x=13

Randy and trey take turns cleaning offices on the weekends. it takes randy at most 4 hours to clean the offices. it takes trey at most 6 hours to clean the offices. what is the greatest amount of time it would take them to clean the offices together? 2.4 hours 2.5 hours