To simplify, put both numbers in fractions
3/5
and
60/1
Then multiply:

Now just multiply across so
3*60=180
and 5*1=5
so you get 180/5
Now divide that
And you get 36
To check your answer, you can do the following.
That is the decimal of 3/5? It is .6
Now if you divide 36/60 you should get the same answer, and it does = .6 so it's correct