Polygon abcde rotates 52º about the origin to create polygon a′b′c′d′e′. if measure of angle bcd equal 31 º , what is the measure of angle b'c'd' ? sorry cant give answers not a multiple choice question

Rotation doesn't change the shape.  The measure of B'C'D' is still 31 degrees

Per means "divide". So meter per second means meter/second.
Also note that a negative power in the numerator is equivalent to a positive in the denominator.
Example:
1/s = s^-1
1/(s^2) = s^-2

Based on this:
100 meters per seconds can be written as:
100 m/s , or
100 ms^-1