Which statement is true about two angles that are complementary

The total cost of anja’s trip to the dentist was $628.35. she paid a flat fee of $89.95 which included the checkup and cleaning and then had 4 cavities filled, each of which cost the same amount. which shows the correct equation and value of x, the cost of each cavity filling?

Find the solution of this system of equation -7x+y=-20 9x-3y=36

Atriangle has a side lengths of 18cm, 80 cm and 81cm. classify it as acute obtuse or right?