Simplest form 9/10-4/10 ?

Jordan rides his bike 6 7/15 miles every day to deliver newspapers and to go to and from school. if his ride to and from school is 4 3/10 miles, how many miles is the trip to deliver newspapers? 1 1/3 1 1/6 2 1/6 2 4/5

If angle b measures 25°, what is the approximate perimeter of the triangle below? 10.3 units 11.8 units 22.1 units 25.2 units

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?