Решите уравнения х+8/15=7/12 x+3/16=17/20 7/30-a=1/12 заранее

х+8/15=7/12 
x = 7/12 - 8/15
x = 0,05
7/12 - 8/15 = 35/60 - 32/60 = 3/60 = 1/20 = 0,05

x+3/16=17/20 
x = 17/20 - 3/16
x = 53/80
17/20 - 3/16 = 68/80 - 15/80 = 53/80

7/30-a=1/12
-a = 1/12 - 7/30
-a = - 0,15
a = 0,15
1/12 - 7/30 = 5/60 - 14/60 = - 9/60 = - 3/20 = - 0,15