What's the fourth multiple of 10

Complete the equation of the line through (−10,3) and (−8,−8). use exact numbers.

Tom wants to order tickets online so that he and three of his friends can go to a water park the cost of the tickets is 16.00 per person there is also a 2.50 one-time service fee for ordering tickets online write an expression in term of n that represents the cost for n ordering tickets online

If f(x) = x+8 and g(x) = 4x- 3, find (f+g)(x)