Find the length of ac. round to the nearest hundredth

Evaluate the dot product of (3,-1) and (1,5)

Asap! i'm not good math and i'm lost.

Ineed big ! the cost of a school banquet is $25 plus $15 for each person attending. create a table, sketch the graph, and write an equation in slope-intercept and point-slope form that gives total cost as a function of the number of people attending. what is the cost for 77 people?