You are close but 1/27 includes people who did not study but still passed. If you want a singular value you should look at the value for the for only the people who studied even if they passed.
Im pretty sure this is correct it has been a while since I did this but y is the total amount so y is 280. M is the slope so it would be how often the amount changes so m is 8. x is unknown and what needs to be solved for. b is the y intercept which is just the initial amount of 130.
