Answer: 8 screws
Step-by-step explanation:
1. You know that Alexis bought 3 boxes of screws with 40 screws in each box, then, to calculate the total number of screws she bought, you must multiply 3 boxes by 40 screws. Then:
[tex]total=3*40\ screws\\total=120 \ screws[/tex]
2. Then, if she had 168 screws and she bought 120, now she has :
168 screws+120 screws=288 screws
3. So to calculate the number of screws that she will have left over when she finishes the deck (which you can call [tex]x[/tex]), you must subtract 288 screws and 280 screws. Therefore, you obtain the following result:
[tex]x=288\ screws-280\ screws=8\ screws[/tex]
