With this plz what is the slope and the y intercept

On #13 it will be the slope formula x1-x2 over y1 - y2 so for #13 it's-6--5 over 12- 14 put that in your calculator and that gives you slope and the y intercept is where the line crosses the y axis or the y line on a graph or you can find the y intercept

How many points are there total? (3*100)+250 = 550

So far, he has 72 + 85 + 78, or 235

He needs 0.80 * 550 for a B, or 440 points

 

440 - 235 = 205 points on the final to get a B

Percentage-wise, he needs 205/250, or 0.82