The GCD of given numbers is 38.
Step 1 : Find prime factorization of each number.
$$\begin{aligned}380 =& 2\cdot2\cdot5\cdot19\\[8pt]266 =& 2\cdot7\cdot19\\[8pt]\end{aligned}$$(view steps on how to factor 380 and 266. )
Step 2 : Put a box around factors that are common for all numbers:
$$\begin{aligned}380 =& \color{blue}{\boxed{2}}\cdot2\cdot5\cdot\color{red}{\boxed{19}}\\[8pt]266 =& \color{blue}{\boxed{2}}\cdot7\cdot\color{red}{\boxed{19}}\\[8pt]\end{aligned}$$Step 3 : Multiply the boxed numbers together:
$$ GCD = 2\cdot19 = 38 $$This solution can be visualized using a Venn diagram.
The GCD equals the product of the numbers at the intersection.