Answer
$\sum_{i=1}^{18}\dfrac{i}{i+2}$
Work Step by Step
For numerators the consecutive numbers starts from number $1$ to $18$ and for denominators the consecutive numbers starts from number $3$ to $20$. Therefore, these numbers can be represented by a summation symbol as:
$\sum_{i=1}^{18}\dfrac{i}{i+2}$
