a, 575 - ( 6.x + 70 ) = 445
6.x + 70 = 575 - 445
6.x + 70 = 130
6.x = 130 - 70
6.x = 60
x = 60 : 6
x = 10
b, x : 125 = 75 dư 5
=> x = 75.125 + 5
=> x = 9375 + 5
=> x = 9380
575 - (6x + 70) = 445
6x + 70 = 575 - 445
6x + 70 = 130
6x = 130 - 70
6x = 60
x = 10