11/12 4/7 7/8 least comon denuminator

In the polynomial below, what number should replace the question mark to produce a difference of squares? x2 + ? x - 36

Anumber cube is rolled two times in a row. find the probability it will land on 2 on the first roll and a number greater then 4 on the second roll

The serenity and the mystic are sail boats. the serenity and the mystic start at the same point and travel away from each other in opposite directions. the serenity travels at 16 mph and the mystic travels at 19 mph. how far apart will they be in 3 hours?