I can't understand this question.

Question

the function f is defined by f(x)=m+x/2+3x for all value of x except when x=h.Find the value of h .

Answer 1

The only way $f(x)$ may possibly be undefined requires that $2+ 3x$ is intended to be a denominator, as in the cases

$$f(x)=m+\frac x{2+3x}\;\text{ and } \;f(x) = \frac{m+x}{2+3x}$$

Denominators cannot be zero, since division by zero is undefined, so in either of the two cases above, $f(x)$ is undefined at any value $x$ at which $2+3x = 0 $.

When is $2 + 3x = 0$?

The solution to this equation is the $h$ you need.