B = (0,75 - 0,6 + 3/7 + 3/13) : (11/7 + 11/13 + 3,75 - 2,2)
= (3/4 - 3/5 + 3/7 + 3/13) : (11/7 + 11/13 + 15/4 - 11/5)
= (3/20 + 3/7 + 3/13) : (220/91 + 15/4 - 11/5)
= (81/140 + 3/13) : (2245/364 - 11/5)
= 1473/1820 : 7221/1820
= 1473/1820 x 1820/7221
= 1473/7221
= 491/2407
Vậy B = 491/2407