min$(a,b)$ is a function that return the minimum of $a,b($assume real numbers$).$ For eg$.,$

is $-1.$

Use case analysis to show that.

min$(a,$min$(b,c))$ is the same as min$(min(a,b),c)$

In other words, it does not matter whether you compare the smaller of $b,c$ with a or compare

$c$ with the smaller of $a,b.$ You get the same answer.