Can someone me with 6b i don't understand it thx if you can

1- what do you think the product of a nonzero rational number and an irrational number is? is it rational or irrational? make use of variables, the closure property of integers, and possibly a proof by contradiction to prove your hypothesis.2- why do we have to specify that the rational number must be nonzero when we determine what the product of a nonzero rational number and an irrational number is? if the rational number were 0, would it give us the same result we found in the first question?

Gabrielle's age is two times mikhail's age. the sum of their ages is 84. what is mikhail's age?

Annabelle's homework is 75% it took her three hours how long should she estimate it will take her to complete her homework.