The number of hours, h, it takes for a block of ice to melt varies inversely as the temperature, t. if it takes 2 hours for a square inch of ice to melt at 70 degrees, find the constant of proportionality

This is an inverse or indirect variation problem that would be set up as y=k/x if you were using y and x.  Since you are using h and t, it would look like this:
h=k/t, where k is the constant of variation. Fill in the formula with the h and the t they give you: 2=k/70. Multiply both sides by 70 to get a constant of variation value of 140.