Can someone help its four questions

Asunflower was 20 1/2 inches tall. over the next 6 months, it grew to a height of 37 inches tall. what was the average yearly growth rate of the height of the plzzz write a proportion i will give you 100 points

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%)

Will give brainliest b. describe the function over each part of its domain. state whether it is constant, increasing, or decreasing, and state the slope over each part.