If you want to calculate -8 < 2/5 * (k - 2), you have to do the following steps to get to know the value of the k.
-8 < 2/5 * (k - 2)
-8 < 2/5 * k - 4/5
-8 + 4/5 < 2/5 * k
-40/5 + 4/5 < 2/5 * k
-36/5 < 2/5 * k
k > -36/5 * 5/2
k > -18
Result: The value of the k is greater than -18.