Since it isn't possible that (3k-4, 16) is going to be equal to (4k, 32) in terms of positive numbers, you will have to go to the negative side of the number line.
K has to equal 4 because 3 · -4 = -12, and -12 minus 4 is equal to -16.
70 has the greatest absolute value because absolute value is the amount between that number and 0. If 70 is the biggest number the with the biggest absolute value is 70.