(1)[1/4]:12=X:[2/5],
12x=[1/4]×[2/5],
12x÷12=[1/10]÷12,
x=[1/120];
(2)[1.25/0.25]=[x/1.6],
0.25x=1.25×1.6,
0.25x÷0.25=2÷0.25,
x=8;
(3)1+25%X=3.25,
1+25%X-1=3.25-1,
25%x÷25%=2.25÷25%,
x=9;
(4)10-15%X=8.5,
10-15%X+15%x=8.5+15%x,
10-8.5=8.5+15%x-8.5,
1.5÷15%=15%x÷15%,
x=10.