A third of a number minus 8 is 17 What is the number

I’m stuck on this i don’t understand.

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

Solve the problem. a student earned grades of c, a, b, and a in four different courses. those courses had these corresponding numbers of credit hours: 4, 5, 1, and 5. the grading system assigns quality points to letter grades as follows: a = 4, b = 3, c = 2, d = 1, and f = 0. compute the grade point average (gpa) and round the result to two decimal places. 3.40 3.50 8.75 2.18