The GCD of given numbers is 5.
Step 1 : Find prime factorization of each number.
$$\begin{aligned}73880 =& 2\cdot2\cdot2\cdot5\cdot1847\\[8pt]55305 =& 3\cdot3\cdot5\cdot1229\\[8pt]50840 =& 2\cdot2\cdot2\cdot5\cdot31\cdot41\\[8pt]\end{aligned}$$(view steps on how to factor 73880, 55305 and 50840. )
Step 2 : Put a box around factors that are common for all numbers:
$$\begin{aligned}73880 =& 2\cdot2\cdot2\cdot\color{blue}{\boxed{5}}\cdot1847\\[8pt]55305 =& 3\cdot3\cdot\color{blue}{\boxed{5}}\cdot1229\\[8pt]50840 =& 2\cdot2\cdot2\cdot\color{blue}{\boxed{5}}\cdot31\cdot41\\[8pt]\end{aligned}$$Step 3 : Multiply the boxed numbers together:
$$ GCD = 5 $$This solution can be visualized using a Venn diagram.
The GCD equals the product of the numbers at the intersection.