问一道初一数学题，数学好的进来！急啊！！

2脳10+(13-9)

(10*2)-(9-13)
((10*2)-9)+13
((10*2)+13)-9
(10*2)+(13-9)
(9-(10-13))*2
((9-10)+13)*2
((9+13)-10)*2
(9+(13-10))*2
(2*10)-(9-13)
((2*10)-9)+13
((2*10)+13)-9
(2*10)+(13-9)
2*(9-(10-13))
2*((9-10)+13)
2*((9+13)-10)
2*(9+(13-10))
2*(13-(10-9))
2*((13-10)+9)
2*((13+9)-10)
2*(13+(9-10))
(13-(10-9))*2
((13-10)+9)*2
13+((10*2)-9)
(13+(10*2))-9
13-(9-(10*2))
(13-9)+(10*2)
((13+9)-10)*2
(13+(9-10))*2
13-(9-(2*10))
(13-9)+(2*10)
13+((2*10)-9)
(13+(2*10))-9

10 × 2 - 9 + 13=24

(9 + 13 - 10) × 2=24

13-9=4,2X10=20,20+4=24

什么意思啊，搞不懂！

共72种:
1: 10 × 2 - 9 + 13
2: (10 × 2) - 9 + 13
3: (10 × 2 - 9) + 13
4: ((10 × 2) - 9) + 13
5: 10 × 2 -(9 - 13)
6: (10 × 2) - (9 - 13)
7: 10 × 2 + 13 - 9
8: (10 × 2) + 13 - 9
9: (10 × 2 + 13) - 9
10: ((10 × 2)