The difference in their speeds is 9.9/11 = 0.9 mi/hr.

The sum of their speeds is 9.9/1 = 9.9 mi/hr.

The sum of their speeds is 9.9/1 = 9.9 mi/hr.

**Roberto's speed is (9.9+.9)/2 = 5.4 mi/hr****Juanita's speed is 5.4 - 0.9 = 4.5 mi/hr.**