a) 7/90 + (¹⁵⁾4/3 - 7/45) - (³⁾1/7 - 1/21) - 11/35 =
7/90 + (60/45 - 7/45) - (3/21 - 1/21) - 11/35 =
⁷⁾7/90 + ¹⁴⁾53/45 - ³⁰⁾2/21 - ¹⁸⁾11/35 =
49/630 + 742/630 - 60/630 - 198/630 =
533/630
b) 17/30 - (³⁾7/10 - ²⁾7/15) - (³⁾23/20 - ²⁰⁾1/3) + 19/10 =
17/30 - (21/30 - 14/30) - (69/60 - 20/60) + 19/10 =
17/30 - 7/30 - 49/60 + 19/10 =
²⁾10/30 - 49/60 + ⁶⁾19/10 =
20/60 - 49/60 + 114/60 =
85/60 = 17/12
c) 8/99 - (¹¹⁾4/9 - ⁹⁾3/11) + (²²⁾1/9 - ⁹⁾1/22) + 14/9 =
8/99 - (44/99 - 27/99) + (22/198 - 9/198) + 14/9 =
²⁾8/99 - ²⁾17/99 + 13/198 + ²²⁾14/9 =
16/198 - 34/198 + 13/198 + 308/198 =
339/198⁽³ = 113/66