if 2 < x < 4 and 1 < y < 3 then find the ratio of the upper limit for x + y and the lower limit of x - y.

Upper limit can be obtained by the combination of upper limits for the terms in addition. So 4+3 = 7. For the lower limit of x-y, in order to get the lowest value, we need to take the lower x and higher y (Trying to get negative numbers, as -ve numbers are least), 2-3 = -1