（1）25x3又1/3x0.4x3/10 =25×0.4×10/3×3/10=10（2）4/7+1/5+3/7+4/5 =(4/7+3/7)+(1/5+4/5)=1+1=2(3)6/7x[1/(5/6-1/2)] =6/7×[1/(5/6-3/6)]=6/7×[1/(2/6)]=6/7×3=18/7(4)4.67-(2.98+0.67）=4.67-2.98-0.67=4-2...