Does commutative property use multiplication and subtraction?

What is the area of triangle abc if a = 8, b = 11, and c = 15?

Name each raycalculation tip: in ray "ab", a is the endpoint of the ray.

Atorch and a battery cost 2.50 altogether. the torch costs 1.50 more than the battery. what fraction of the total price is the torch? give your answer in its simplest form.