2. You can set the remainder as a and two digits as b, then b=7a+a, then the minimum value is 7* 1+ 1=8, and the maximum value is 7* 12+ 12=96.

3.6 tons of big trucks and 4 tons of small trucks.

4. Class A includes B volleyball and C basketball, so 2a+ 1=b 8a-5=c 3b=c, a=4 b=9 c=27.

I can't see where your formula is!

6. Let the number be ab, so a0b-ab=630, which is converted into a00-ao=630, that is, A0-A = 63 and A = 7, so * * * is 1.

7. From 48a=b 60*(a-5)=b, a=25 b= 1200, that is, *** 1200.

8 、[({[(a/2+ 1)/2+ 1]/2+ 1 }/2+ 1)]/2+ 1 = 3 a = 34

9. You can open the calendar. A little trouble!

10. Years ago was X years, and my sisters were A and B, so a+b=55 a-x=b b-x=a/2. My elder sister a=220/7=3 1. 1 (rounded) is 23 years old.

1 1 students, 5a+3=b 6(a-2)+8=b a=7 pit b=38.

12 and 12 floors

13, 1*3+2+5+ 10=20 minutes.

14, Xiaowu 136, hit 8 rounds; Meng learned 72 points and played six rounds.

15, a/ 12= 12, so a= 144, so a/( 12-3)= 15 hours.

16, none

17,84 (x-1)+100/x=86, x = 8 times.

18，A 2 B 2 C 3 D 1