How do you write an equation in slope intercept form with the points (5,19) (-9,5)

How do you determine whether a relationship represented as as graph is linear or nonlinear

Write the function for the graph. (1.8) (0,4)

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?