Im doing triangles in class right now and i don't know how to find out if its a right triangle let alone find if its a 90 * how do i find it?

All right triangles follow the pythagorean theorem. One way to tell if a triangle is a right triangle is by plugging all three side lengths into the pythagorean theorem:

a^2 + b^2 = c^2

(a and b being legs, c being the hypotenuse).

If the equation works, the triangle is right. If the equation is false, the triangle is not right.