2.脱式计算。(能简算的要简算)(9分)-|||-times dfrac (97)(99)-|||-dfrac (10)(21)times dfrac (7)(20)div dfrac (5)(6)+dfrac (1)(4)-|||-.https:/img.zuoyebang.cc/zyb_a40dc135bde5955229f293b1ac51fe36.jpg-dfrac (5)(8)div dfrac (25)(28)-dfrac (3)(10)