Split String and Do Calculation in MySQL

Let's say I have given data as string:

+----------+
|Size      |
+----------+
|15X10     |
|5X4       |
|3         |
|2X6X5     |
+----------+

I want to write this column as integer like this:

 +----------+
 |Size      |
 +----------+
 |150       |
 |20        |
 |3         |
 |60        |
 +----------+

Some of them are multiply of three numbers, some of them just one number. I can split the string but cannot make MySQL to calculate the number. Thank you.