p(x=3)= 5!/3!(5-3)!

You both should have enclosed the bottom (denominator) in brackets!

due to me being a dumber i dont know exactly what youre asking but i do know how to solve 5!/3!(5-3)!

given how you asked i figure you know how factorials work

5!=120
3!=6
(5-3)!=2!=2
120/6*2=120/12
120/12=10/1=10

5!/3!(5-3)!=10