答案就是这样的7.2×4.6+4.6×12.71=91.586
7.2×4.6+4.6×12.71=4.6×（7.2+12.71）=4.6×19.91=4.6×（20-0.09）=4.6×20-4.6×0.09=92-4.6×（0.1-0.01）=92-0.46+0.046=92-（0.46-0.046）=92-0.414=91.586
