Can someone help me please only do it if you know geometry

The center of the circumscribed circle lies on line segment and the longest side of the triangle is equal to the of the circle.

Aconstruction worker has rope 9 m long he needs to cut it in pieces that are each 3 /5 m long how many such pieces can he cut without having any rope leftover?

Whats are the trickiest steps to do when adding or subtracting rational expressions? how does knowledge of rational numbers u in adding and subtracting rational expressions?