Answer :

12 x 5.2

Estimate:
since 5.2 is about 5, we can estimate this to:
12 x 5 = 60

Find the Product: 
    
        12
  x    5.2  
        2 4
  +  6 0 0
       6 2 4

now add the decimal back in. In the original problem there is one decimal place (the .2 in 5.2) so we move the decimal place one over in our product

624 becomes 62.4