What is the nearest hundred to 12.5

Which shows the correct solution of the equation 1/2a+2/3b=50, when b=30?

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?

With number 11 ( show how you got the answer)