请教几道数学题（列式计算）①2/3与1/2的和去除2/3与1/6的差,商是多少?②一个数的1/2比它的4/5少30,这个数是多少?③甲数的25%等于乙数的2/3,乙数是72,甲数是多少?④一个数是36,另一个数是它的5/12,则这两个数的和是多少?⑤一个数的4倍减去这个数的本身,差是42.6,求这个数.⑥某数的4/9比6/5的5/4倍多21/10,这个数是多少?⑦一个数的1/2加上1/2的倒数,和是3,这个数是多少?⑧15的2/3比一个数的4倍少12,这个数是多少?⑨1/5与1/6的和除以它们的差,商是多少?

①(2/3+1/2)/(2/3-1/6)=7/12
②30/(4/5-1/2)=100
③72*2/3/25%=192
④36*(1+5/12)=51
⑤42.6/(4-1)=14.2
⑥(21/10+6/5*5/4)/4/9=81/10
⑦(3-2)/1/2=2
⑧(15*2/3+12)/4=5.5
⑨(1/5+1/6)/(1/5-1/6)=11

(2/3+1/2)/(2/3-1/6)=7/3
30/(4/5-1/2)=100
72*2/3/25%=192
36*(1+5/12)=51
42.6/(4-1)=14.2
[(6/5)*(5/4)+21/10]/(4/9)=81/10
[3-1/(1/2)]/(1/2)=2
(15*2/3+12)/4=5.5
(1/5+1/6)/(1/5-1/6)=11

1. (2/3 +1/2)/(2/3 -1/6) = (4/6+3/6)/(4/6 -1/6) = (7/6)/(3/6) = 7/3
2. 30/(4/5 - 1/2) = 30/(8/10 - 5/10) = 30/(3/10) = 100
3. (72*2/3)/25% = 48/25% = 192
4. 36 + 36*5/12 = 36 + 15 = 51
5. 42.6/3 = 14.2
6. 4a/9 - (6/5)*(5/4) = 21/10, 4a/9 = 21/10 + 3/2 = 21/10 + 15/10 = 36/10 = 18/5
a = (18/5)*(9/4) = 81/10
7. a/2 + 1/(1/2) = a/2 + 2 = 3, a/2 = 1, a = 2
8. 4a - 15*2/3 = 12, 4a - 10 = 12, 4a = 22, a = 11/2
9. (1/5 + 1/6)/(1/5 -1/6) = (6/30 + 5/30)/(6/30 - 5/30) = (11/30)/(1/30) = 11