Tolong dong ! Gimana caranya

(a) 180 = x + 60 +80
180 = x + 140
x = 40
(b) 180 = 30 + 25+ x
180 = 55 + x
x = 125
(c) 180 = (360-290) + 55 + x
180 = 70 + 50 + x
180 = 120 + x
x = 60
(d) 180 = (180-99) + 42 + x
180 = 81+42+x
180 = 123 + x
x. = 57