Multiply 1/3 by 4 and 1/4 by 3 so the denominators are both 12. Then you have 4/12 and 3/12 so add those two fractions to get 7/12. if all three days equals 12/12, and Monday plus Tuesday equals 7/12, the remainder of the pay will be 5/12 on Wednesday.
No, the least amount of points you can do on a graph to see the pattern is 3 because than you can get a better line for your graph to see what kind of pattern your graph is.