①30%x+45%x=3,
(30%+45%)x=3,
0.75x=3,
0.75x÷0.75=3÷0.75,
x=4;
②(1+10%)x=1.32,
1.1x=1.32,
1.1x÷1.1=1.32÷1.1,
x=1.2;
③12-25%x=10,
12-0.25x+0.25x=10+0.25x,
10+0.25x=12,
10+0.25x-10=12-10,
0.25x=2,
0.25x÷0.25=2÷0.25,
x=8;
④x÷25=
,1 5
x÷25×25=
×25,1 5
x=5.