Дроби писать буду через /, например 1/2 - одна вторая, если есть целое, то будет выглядеть так 1 1/2 - между целым и дробью пробел, одна, целая одна вторая
1) 7/12у = 1 1/4
у = 5/4 : 7/12
у = 5/4 * 12/7
у = 15/7
у = 2 1/7
2) 3 1/15 - 1 14/15а = 1/6
1 14/15а = 3 1/15 - 1/6
1 14/15а = 3 4/60 - 10/60
1 14/15а = 2 54/60
1 14/15а = 2 9/10
а = 2 9/10 : 1 14/15
а = 29/10 * 15/29
а = 2/3
а = 1 1/2
3) (17/18 + 5/24х) : 3 2/3 = 1/3
1718 + 5/24х = 1/3 * 3 2/3
17/18 + 5/24х = 1/3 * 11/3
17/18 + 5/24х = 11/9
5/24х = 11/9 - 17/18
5/24х = 22/18 - 17/18
5/24х = 5/18
х = 5/18 : 5/24
х = 5/18 * 24/5
х = 4/3
х = 1 1/3
4) 4/7х + 5/14х - 10/21х = 1/7
8/14х + 5/14х -10/21х = 1/7
13/14х - 10/21х = 1/7
39/42х - 20/42х = 1/7
19/42х = 1/7
х = 1/7 : 19/42
х = 1/7 * 42/19
х = 3/19
5) m - 5/12m = 1/4
12/12m - 5/12m = 1/4
7/12m = 1/4
m = 1/4 : 7/42
m = 1/4 * 42/7
m = 3/7
6)1 1/9m + 5/6 = 1 1/2
1 1/9m = 1 1/2 - 5/6
1 1/9m = 1 3/6 - 5/6
1 1/9m = 4/6
m = 4/6 : 1 1/9
m = 4/6 : 10/9
m = 4/6 * 9/10
m = 3/5
7) m : 5 2/3 = 1 7/9 : 1 7/27
m : 5 2/3 = 16/9 : 34/27
m : 5 2/3 = 16/9 * 27/34
m : 5 2/3 = 24/17
m = 24/17 * 5 2/3
m = 24/17 * 17/3
m = 8
8) |у - 9| = -4, т.к. -4 < 0, то уравнение не имеет корней
9) -7/15х - 3 = 1 2/3
-7/15х = 1 2/3 + 3
-7/15х = 4 2/3
х = 4 2/3 : (-7/15)
х = 14/3 * (-15/7)
х = -10
10) -0,2х * (-0,7) = 0,84
-0,2х = 0,84 : (-0,7)
-0,2х = -1,2
х = -1,2 : (-0,2)
х = 6