the first thing you would have to do is put the numbers in numerical order, starting from the lowest. So, 70, 80, 83, 86, 88, 88. Then, you have to start crossing the numbers off, cutting 70 and the last 88. So now you have 80, 83, 86, and 88. Repeat the process, crossing off 80 and 88. Now you are left with 83 and 86. In this case, all you have to do is find the middle of these two numbers. Since 86-83=3, take 3 and divide it by two, which gives you 1.5. Simply add 1.5+83, and that gives you 84.5. Hope that helps. :)