标签：5x1

7.5x0.8+1.2x12.5+2.5x1.6简便计算如下：7.5x0.8+1.2x12.5+2.5x1.6=0.8×7.5+2.5×2×0.8+1.2×12.5=7.5×0.8+5×0.8+1.2×12.5=（7.5+5）×0.8+1....