解：依题意得算式，4.8-2.3×12.50×（0.8+0.4）=4.8-2.3×（12.5×0.8+12.5×0.4）=4.8-2.3×（10+5）=4.8-（2.3×10+2.3×5）=4.8-（23+11.5）=4.8-34.5=-29.7即4.8-2.3×12.50×（0.8+0.4）=-29.7
