Answer:
Both are correct. Gavin just took more steps to get his answer.
Explanation:
Briana's work:
20x23=460
522-460=92
4x23=92
92-92=0
24x23=552
Gavin's work:
10 x 23=230
552-230=322
10x23=230
322-230=92
2x23=46
92-46=46
46-46=0
24x23=552.
Hope this helps :)