What is the value of my num after the following statements execute?

my$\_$num $=5$

my$\_$num $+=20$

my$\_$num $-=12$

my$\_$num $*=0\mathrm{.}5$

$0\mathrm{.}5$

$6$

$6\mathrm{.}5$

$12\mathrm{.}5$