Here's another one:

3.1 x 5.9

Before we get into it, what should our answer be close to?  Do some rounding...  3 x 6 = 18...  So, our answer should be around 18!

Here we go!

Multiply...  Count the spots behind the decimals...  Put the decimal point in your answer:

3.1 x 5.9 = 18.29

Let's do one more...

2.35 x 7.8

Multiply...  Count the spots behind the decimals...  Put the decimal point in your answer:

2.35 x 7.8 = 18.33