1. 0,25х +0,4х=7-0,35;
0,65х=6,65;
Х=6,65:0,65; х=665/100*100/65;
Х=665/65=10 3/13;///
2. 4(2,5-х)-4,5=12,5;
4(2,5-х)=12,5+4,5;
2,5-х=17/4;
-х=4 1/4-2 1/2;
-Х=17/4-10/4;
Х=-7/4; х=-1 3/4;/////
3. 0,3х-0,8х+5=х-4;
-0,5х-х=-4-5;
-1,5х=-9;
Х=-9:-1,5;
Х=6;////
4. 2,5х+9,5=3-х;
2,5х+х=3-9,5;
3,5х=-6,5;
Х=-6,5:3,5;
Х=-65/35;
Х=-1 6/7