Which best describes Earth’s magnetic field lines?

Twice the sum of a number and 4 is equal to three times the difference of the number and 7. find the number.

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?

Having a hard time understanding this question (see attachment).