Hi. can someone help me with this? i’m confused

Hello everybody. can anybody me come up with detailed study plan on what topics to study from algebra 1 & 2, trig, and any other topic nesscery for success as a new beginner in pre-calculus. i dont have much math history but the basics. this will greatly me.

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%)

Yvaries directly as x. y =90 when x=6. find y when x=13