If x is greater than or equal to 25 and y is less than or equal to 40, then which one of the following is always correct?

Answer is (c). Given that x is greater than or equal to 25. Also, y is less than or equal to 40. Let’s try to find the various values of y – x. If y = 40, x can take various values like 25, 26, 27, ....... (not necessarily integers – not given in question) In that case y – x will take values like 15, 14, 13, 12,......0, - 1 etc. If y = 39, x can take various values 25, 26, 27.... (not necessarily integers) In that case y – x will take values like 14, 13, 12, 11 ..... 0, - 1 etc. Similarly, if y = 38, values of y – x will be 13, 12, 11, ..... 0, -1 etc. and so on. So, we can say that value of y – x is less than or equal to 15 in all cases.