Multiply it as if there weren't a decimal. That would be 786 times 46. Then, however many digits there were after the decimal, you count that many times from where the decimal is in your previous answer, in this case, 3. Let me demonstrate. Here is an example.
123.45 x 10
Take away the decimal(s).
12345 x 10
Multiply.
123450
There were 2 numbers after the decimal(s). So move the decimal 2 digits to the left.
123450. Turns Into 1234.50 Which Is The Same As 1234.5