17/7×24/9+17/9×24/5
=17*24/(7*9)+17*24/(9*5)
=17*8/3(1/7+1/5)
=17*8/3*(5+7)/35
=17*8*12/(3*35)
=17*8*4/35
=17*32/35
=544/35
99又5/1×4/5
=(100-4/5)*5/4
=25*5-1
=125-1
=124
0.375×91/2+91/3×8/11
=3/8×91/2+91/3×8/11
=91*(3/4+8/33)
=91*(3*33+4*8)/132
=91*131/132
=98.25