What is the center of dilation a, b,c, or d

Two cyclists 84 miles apart start riding toward each other at the same. one cycles 2 times as fast as the other. if they meet 4 hours later, what is the speed (in mi/h) of the faster cyclist?

Which expression shows the sum of the polynomials with like terms grouped together

Plz ( true - false) all triangles have interior angles whose measure sum to 90.