How do you prove a triangle is a right triangle with coordinates?

Afrequency table of grades has five classes (a, b, c, d, f) with frequencies of 3, 13, 14, 5, and 3 respectively. using percentages, what are the relative frequencies of the five classes?

You buy a veido game for $60 and the sales tax is 8% what is the total cost for the game including the sales tax

7+(3n++8) what is the answer to this?