In this case, "linearize" means to find a straight line that best fit the given data.  You can plot the data on graph paper and eyeball a line that's close to the points (one of the methods is to pick two points and draw a line through them, but it may lead to very bad approximations).  Then the meaning of "best fit" and "close to the points" should be specified quantitatively.  I think the website you got the problem from should have certain criteria.  If they don't have it, then you can try searching for "least square regression" as one of the possible ways.