The GCD of given numbers is 12.
Step 1 : Find prime factorization of each number.
$$\begin{aligned}36 =& 2\cdot2\cdot3\cdot3\\[8pt]60 =& 2\cdot2\cdot3\cdot5\\[8pt]\end{aligned}$$(view steps on how to factor 36 and 60. )
Step 2 : Put a box around factors that are common for all numbers:
$$\begin{aligned}36 =& \color{blue}{\boxed{2}}\cdot\color{red}{\boxed{2}}\cdot\color{Fuchsia}{\boxed{3}}\cdot3\\[8pt]60 =& \color{blue}{\boxed{2}}\cdot\color{red}{\boxed{2}}\cdot\color{Fuchsia}{\boxed{3}}\cdot5\\[8pt]\end{aligned}$$Step 3 : Multiply the boxed numbers together:
$$ GCD = 2\cdot2\cdot3 = 12 $$This solution can be visualized using a Venn diagram.
The GCD equals the product of the numbers at the intersection.