Я не понимаю дроби, плиз, помогите!!

1)
-7/11 * 1 5/17 : (-0,75) = 7/11 * 22/17 : 3/4 = 7/11 * 22/17 * 4/3 = 56/51 = 1 5/51,
2) 
(1,2 - 2 7/25) : 1 2/25 + 1 4/13 =
(12/10 - 57/25) : 27/25 + 17/13 = (60/50 - 114/50) * 25/27 + 17/13 = 
54/60 * 25/27 + 17/13 = 5/6 + 17/13 = 65/78 + 85/78 = 150/78 = 1 12/13,
3)
(4,25*16/51 - 17/18:8,5) * (3/11) = 
(17/4*16/51 - 17/18*2/17) * 9/121 = 
(4/3 - 1/9) * 9/121 = 
(12/9 - 1/9) * 9/121 = 8/9 * 9/121 = 8/121,
4)
(-12,6*1 1/9 + 10,8) : 6 6/7 + 2 3/10 = 
(-126/10*10/9 + 108/10) : 48/7 + 23/10 = 
(14/3 + 108/10) * 7/48 + 23/10 = 
(140/30 + 324/30) * 7/48 + 23/10 = 
464/30 * 7/48 + 23/10 = 
203/90 + 23/10 = 203/90 + 207/90 = 
410/90 = 41/9 = 4 5/9