Sugar Rounds Donut Shop offers 2 free donuts with every 20 purchased donuts. Sweet Delights Donut Shop offers 3 free donuts with every 30 purchased donuts. Which donut shop offers a greater ratio of free donuts to purchased donuts?

Astudent must have an average on five test that is greater than it equal to 80% but less than 90% to receive a final grade of b. devon's greades on the first four test were 78% 62% 91% and 80% what range if grades on the fifth test would give him a b in the course? ( assuming the highest grade is 100%)