We can multiply the numbers without the decimal point first (that is to say 753 x 42):
7 5 3
× 4 2
-------------
1 5 0 6
+3 0 1 2
-----------------
3 1 6 2 6
After getting the result we must move the decimal point as many positions to the left as decimal digits we find in both numbers. 7.53 has two decimal digits and 0.42 has two decimal digits. Therefore, they have in total 4 decimal digits, so we have to move the decimal point 4 positions to the left from the right side of the number 31626.
Therefore the answer would be 3.1626