There are 5 milliliters of compound a used for every 4 milliliters of compound b. if a chemist wants to make 495 milliliters, how many milliliters of compound a are needed

275

Step-by-step explanation:

Since there are 4 mm of B for every 5 mm of A that means there are 9 parts in that. Dividing 495 by 9 you get 55 which is how much of each part of the compound there is. Since there are 5 mm of A in each part of A you multiply 5 by 55 to get 275 which is your answer.

19. -3/4
20. 2/1= 2

Explanation: I used rise/run. Leftward facing is positive and rightward is negative. When the line perfectly intersects with a point you go up or down based on if positive or negative to the line of the next point that perfectly intersects. Then you go over to the same point, that’s run. So you’ll get rise/run.