For the second one, first recall what the Intermediate Value Theorem says.
Basically, if g(x) is a continuous function on the interval [a,b] and g(a) < 0 < g(b), then there is some value c in the interval [a,b] such that g(c) = 0.
In other words, if the function crosses the x-axis on [a,b], there is an x value that makes this possible.
We want to know which interval does NOT allow us to make this conclusion for g(x) = -3tan(x).
First, I’d calculate g(a) and g(b) for a given interval.
Then, if 0 lies in between g(a) & g(b), you discard that option (ask yourself why?) and move on to to the next one.
You’ll get the answer once you find the interval where 0 does not lie in between g(a) and g(b).