The GCD of given numbers is 26.
Step 1 : Find prime factorization of each number.
$$\begin{aligned}104 =& 2\cdot2\cdot2\cdot13\\[8pt]130 =& 2\cdot5\cdot13\\[8pt]\end{aligned}$$(view steps on how to factor 104 and 130. )
Step 2 : Put a box around factors that are common for all numbers:
$$\begin{aligned}104 =& \color{blue}{\boxed{2}}\cdot2\cdot2\cdot\color{red}{\boxed{13}}\\[8pt]130 =& \color{blue}{\boxed{2}}\cdot5\cdot\color{red}{\boxed{13}}\\[8pt]\end{aligned}$$Step 3 : Multiply the boxed numbers together:
$$ GCD = 2\cdot13 = 26 $$This solution can be visualized using a Venn diagram.
The GCD equals the product of the numbers at the intersection.