（1）49.5×10又3/5-(50-1/2)×0.6
=49.5×10.6-49.5×0.6
=49.5×（10.6-0.6）
=49.5×10
=495
（2）91×1/13-1÷13×100+9÷13
=（91-100+9）×1/13
= 0×1/13
=0
（3）2×1/5+5×2/11+4×2/5+3×4/11
=（2+8）×1/5+（10+12）×1/11
=10×1/5+22×1/11
=2+2
=4