а) 400 : t - 32 = 48
400 : t = 48 + 32
400 : t = 80
t = 400 : 80
t = 5
б) 250 + 9 * a = 520
9 * a = 520 - 250
9 * a = 270
a = 270 : 9
a = 30
в) (780 - m * 60) : 6 = 70
780 - m * 60 = 70 * 6
780 - m * 60 = 420
m * 60 = 780 - 420
m * 60 = 360
m = 360 : 60
m = 6
г) 640 : (x * 9 + 8) = 8
x * 9 + 8 = 640 : 8
x * 9 + 8 = 80
x * 9 = 80 - 8
x * 9 = 72
x = 72 : 9
x = 8