Which of the following equations have no solutions?
choose all answers that apply:
choose all answers that apply:

(choice a)
a
-40x+40=20x+20−40x+40=20x+20minus, 40, x, plus, 40, equals, 20, x, plus, 20

(choice b)
b
20x+40=40x+2020x+40=40x+2020, x, plus, 40, equals, 40, x, plus, 20

(choice c)
c
-20x+40=-20x+20−20x+40=−20x+20minus , 20, x, plus, 40, equals, minus, 20, x, plus, 20

(choice d)
d
40x+40=40x+2040x+40=40x+20