①720-256-44
=720-(256+44)
=720-300
=420
②243×104-243×4
=243×(104-4)
=243×100
=24300
③125×56
=125×8×7
=1000×7
=7000
④158+36+42+264
=(158+42)+(36+264)
=200+300
=500
①720-256-44
=720-(256+44)
=720-300
=420
②243×104-243×4
=243×(104-4)
=243×100
=24300
③125×56
=125×8×7
=1000×7
=7000
④158+36+42+264
=(158+42)+(36+264)
=200+300
=500