Fill in the missing operator where the blank is (-40)__(8)=-5

How do you find principle and simple interest

Dean and karlene get paid to write songs. dean is paid a one-time fee of $20 plus $80 per day. karlene is paid a one-time fee of $25 plus $100 per day. write an expression to represent how much a producer will pay to hire both to work the same number of days on a song.

Tan198=asin164=? how to solve this? ?