Could someone help with this math question brainlest and 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%)

Larger pets need to be transported in larger portable kennels. using a graphing calculator and the relationship between the width, length, and height, find the dimensions of a portable kennel whose volume is 7.4 ft3. the dimensions of a portable kennel can be expressed as width x, length x + 0.4, and height x − 0.2? what are the dimensions of a portable kennel with a volume of 7.4 ft3? use a graphing calculator to solve. round the dimensions to the nearest tenth.

If m is the midpoint of ln and ln=27.8 find the length of mn