(1)83*77
解原式=（80+2）(80-3)
=6400-9
=6391
(2)1.2²*9-1.3²*4
解原式=(1.2×3-1.3×2)(1.2×3+1.3×2)
=(3.6-2.6)(3.6+2.6)
=1×6.2
=6.2
(3) 16.8*15/32+7.6*15/16
解原式=15/16（16.8×1/2+7.6）
=15/16（8.4+7.6）
=(15/16)×16
=15