20. state whether the conjecture is true or false. if false, provide
counterexample.
subtraction of whole numbers is commutative.

Element x decays radioactively with a half life of 8 minutes. if there are 450 grams of element x, how long, to the nearest tenth of a minute, would it take the element to decay to 37 grams?

Due to bad planning, two of the local schools have their annual plays on the same weekend. while 457 people attend one, and 372 attend the other, only 104 people were able to attend both. how many people went to at least one play?

Micheal is 4 times as old as brandon and is also 27 years older than brandon. how old is micheal