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.