1.4.2c Finding a new function given a composite function (Case B : Second function is given) Example 3

Example 3 (Substitution Method)
A function f is defined by

f : x \mapsto \frac{7}{x}

.
Find the function g if

g f : x \mapsto \frac{10}{2 x + 3}, x \neq - \frac{3}{2}

.

[Note : Second function is given, use substitution method]