To multiply decimals is just like multiplying regular numbers, just a few extra steps here and there. :)
1) Set up your problem just as you would with any problem. Don't like up the decimals, ignore them as if they weren't there but include them.
2) Start by multiplying 2 x 3, which equals 6. Then 2 x 5 which equals 10, and 7 x 2 which equals 14, plus 1 is 15 (Remember- carry).
1
75.3
x .42
1506
3) Now continue.
75.3
x .42
1506
+3012
4) Add 1506 + 3012.
1
75.3
x .42
1506
+3012
31626
5) Take a look at the digits to the right of the decimal point. Add the total up. There are 3 in total.
6) Move the decimal point in 31626 3 times to the left.
31.626
That is your answer!