Each day, there is a 75% chance that elise will do her homework. what is the probability she does her homework on monday or tuesday?

This problem is easier solved by finding the probability that she does NOT do her homework both Monday and Tuesday, which is obtained by the multiplication rule.

P (no HW on Monday) = 1-0.75 = 0.25

P (no HW on Tuesday) = 1-0.75 = 0.25

P (no HW on both Monday and Tuesday) = 0.25*0.25=0.0625

[by the multiplication rule]

This means that the rest of the time (1-0.0625=0.9375) Elsie does her homework either Monday, or Tuesday, or both days.

=>

P (HW either Monday, Tuesday, or both) = 0.9375

(note: in current English, Monday or Tuesday means "either Monday, Tuesday, or both days")