1. The problem is to evaluate the expression $20 \checkmark$. 2. The symbol \checkmark is not a standard mathematical operator. It might be a typo or a symbol used in a specific context. 3. If you meant the square root, the symbol is usually $\sqrt{}$. If you meant factorial, the symbol is $!$. 4. Assuming you meant the square root, the problem becomes $\sqrt{20}$. 5. The formula for the square root is $\sqrt{a}$ which means a number that when multiplied by itself gives $a$. 6. Calculate $\sqrt{20} = \sqrt{4 \times 5} = \sqrt{4} \times \sqrt{5} = 2\sqrt{5}$. 7. $\sqrt{5}$ is an irrational number approximately equal to 2.236. 8. So, $\sqrt{20} \approx 2 \times 2.236 = 4.472$. 9. If you meant factorial, $20!$ is the product of all positive integers from 1 to 20, which is a very large number. 10. Please clarify if you meant something else by the symbol \checkmark.