Question

For what values of the variable does the following expression make sense:

Answer 1

This question revolves around the concept of domain (primarily) and range (secondarily).  The domain of the square root function is [0, +infinity).

The domain of "three times the sqrt of a" shares that domain:  [0, +infinity).

We were not asked to come up with the range, but if the range is wanted, it is

[0, +infinity).