Given a positive integer $G$ and a list of $N$ other positive integers, this question asks to find the number of integers in the list which are multiples of $G$. The solution is to just loop through the list and check if each integer is a multiple of $G$. If so, increment a running counter variable.

Checking if a number $F$ is a multiple of $G$ can be done with the modulo (or remainder) operator in most programming languages (the % operator in C++/Java/Python, for instance). That is, $F$ is a multiple of $G$ if and only if $F\mathrm{\%}G$ is equal to $0$. Since we loop through an array of size $N$, this runs in $\mathcal{O}(N)$.