Đáp án:

 `A=\frac{7}{145764}`

Giải thích các bước giải:

 Bài `1:`

`a)A=\frac{(17 21/56-13 21/45):(3/4+11/30)}{9^{3}.100-2.3^{2}}`

`=\frac{[17+21/56-(13+21/45)]:(45/60+22/60)}{(3^{2})^{3}.2.50-2.3^{2}}`

`=\frac{(17+3/8-13-7/15): 67/60}{2.3^{2}.[(3^{2})^{2}.50-1]}`

`=\frac{(4+3/8-7/15): 67/60}{2.9.(9^{2}.50-1)}`

`=\frac{(\frac{480}{120}+\frac{45}{120}-\frac{56}{120}): 67/60}{18.(81.50-1)}`

`=\frac{\frac{469}{120}. \frac{60}{67}}{18.(4050-1)}`

`=\frac{\frac{109}{134}}{18.4049}`

`=\frac{7}{2}:(18. 4049)`

`=\frac{7}{2}: 72882`

`=\frac{7}{2}.\frac{1]{72882}`

`=\frac{7}{2.72882}`

`=\frac{7}{145764}`

Vậy `A=\frac{7}{145764}`