Turn them into mixed fractions first:
3 1/2 = 7/2 and 4 2/3 = 14/3 
Then multiply the fractions: 
7/2 x 14/3 
Make sure you multiply the denominators together and multiply the numerators together, straight across. 
7/2 x 14/3 = 98/6 
Now simplify!
98/6 = 16 2/6 = 16 1/3
That’s your answer, 16 1/3