3(1/8)*7.4-3(1/8)+3.6*3.125 (0.125=1/8)=3.125*(7.4-1+3.6)=3.125*10=31.25 或 31(1/4)3又50分之7就是3.14原式=3.14*（4.3+7.2-10.5）=3.14*1=3.141/【n（n+1）】=1/n-1/（n+1）所以原式=1/1-1/2+1/2-1/3……+1/20...3(1/8)*7.4-3(1/8)+3.6*3.1253.125素3.25叭？。。。。要素3.125窝都会捏~要么就素题印错了、那就是=3.125*7.4-3.125+3.6*3.25=23.125-3.125+11.7=31.7052题2.解10(4/5)-（8.8-5/7）+2/7=10.8-8.09+0.29=3