Ответ:

(5•a-25)/4 = 29 - 4•6

(5•a-25)/4 = 5

5•a = 45

a = 9

39+a (42/7) - (19+18) = 26

39+a•6-37=26

a•6=24

a=4

(470+430)/3-x/5=100

900/3-x/5=100

300-x/5=100

-x/5=-200

x=1000

7•x+(1270-30)/4=366

7•x+310=366

7•x=56

x=8