Решите уравнения:

а) x + 4/15 = 2/3 + 2/5

б) ( 4/5 - x ) + 13/20 = 25/30

в) y – 5/20 = 5/8 – 3/10

г) 2/3 – ( 7/9 – а ) = 1/3

а) x + 4/15 = 2/3 + 2/5

х=2/3+2/5-4/15

х=10/15+6/15-4/15

х=12/15

х=4/5

б) ( 4/5 - x ) + 13/20 = 25/30

4/5-х=25/30-13/20

4/5-х=50/60-39/60

4/5-х=11/60

х=4/5-11/60

х=48/60-11/60

х=37/60

в) y – 5/20 = 5/8 – 3/10

у=5/8-3/10+5/20

у=25/40-12/40+10/40

у=23/40

г) 2/3 – ( 7/9 – а ) = 1/3

2/3-7/9+а=1/3

а=1/3-2/3+7/9

а=3/9-6/9+7/9

а=4/9