a=b a-c=b-c c=d a-c=b-d
Work Step by Step
a=b is given in the question. Because a=b then if the same amount (c) is taken from both a and b, the two sides will still be equal. Therefore a-c=b-c. c=d is given in the question. If c=d then d can replace c in any equation, therefore b-c=b-d. We already know that a-c=b-c, therefore a-c=b-d as well. Therefore a-c=b-d is proved.