7.68×2.4-0.214×24=7.68×2.4-2.14×2.4=2.4×(7.68-2.14)=2.4×5.54=2.4×(5+0.5+0.04)=2.4×5+2.4×0.5+2.4×0.04=12+1.2+0.096=13.296