The first step is to write each factor in expanding notation.
This is:
- 124 = 100 + 20 + 4
- 2 = 2
Now muliply 2 times each term of the terms 100, 20 and 4
=> 2 * 100 = 200
2 * 20 = 40
2 * 4 = 8
Then,
(100 + 20 + 4 )
x 2
-----------------------
8
40
200
------------------------
248