If a > b and k is a positive number, which of the following is not true? explain why. a. a + k > b + k b. a - k > b - k c. k - a > k - b

The answer is C.

explanation:
A, since the equations are added by the same number on both sides, A stays a higher number than B.
B, since they are subtracted by the same number, A still stays a higher number than b.

C, however, is different. now that the numbers are being subtracted FROM a number, the above would no longer be true. say A was 10 and B was 7. k is 5.
A- 5-10= -5
B- 5-7= -2
now B is a higher number than A, so C is no longer true.