3/7x1/4+1/7x0.25=1/4x(3/7+1/7)=1/7
1.2x(5/12-5/42)=6/5x5/12-6/5x5/42=1/2-1/7=5/14
2.5%*8+(1/3÷2/3)=1/5+1/3x3/2=7/10