(1/4 + 3/4х) : 0,45 = 25/36
1/4 + 3/4х = 25/36 * 0,45
1/4 + 3/4х = 25/36 * 9/20
1/4 + 3/4х = 5/16
3/4х = 5/16 - 1/4
3/4х = 5/16 - 4/16
3/4х = 1/16
х = 1/16 : 3/4
х = 1/16 * 4/3
х = 1/12
Пояснения:
0,45 = 45/100 = 9/20 - сократили на 5
25/36 * 9/20 = (5*1)/(4*4) = 5/16
1/4 = 4/16 - доп.множ. 4
1)=-2х-3у
2)=8х-4у
3)5а-10=10
5а=10+10
5а=20
А=20:5
А=4
4)2с-5с=1,2-3,6
-3с=-2,4
С=-2,4:(-3)
С=0,8
5)-3х-4х=56-14
-7х=42
Х=42:(-7)
Х=16
1) 3/4х+6=2/3х-9
3/4х-2/3х=-9-6
9/12х-8/12х=-15
1/12х=-15
Х=-15:1/12=-15*12
Х=-180