用简便方法计算 (+18)+(-24)-(-15) (-3/4)-(-三又八分之三）+3/4-五又二分之一+二又八分之五

①(+18)+(-24)-(-15)
=18-24+15
=18+15-24
=33-24
=9
②(-3/4)-(-三又八分之三）+3/4-五又二分之一+二又八分之五
=-3/4+3又3/8+3/4-5.5+2又5/8
=（3/4-3/4）+（3又3/8+2又5/8）-5.5
=0+6-5.5
=0.5