Two numbers a? b are chosen from the set of integers 1, 2, 3, .…. 39.Then probability that the equation 7a - 9b = 0 is satisfied is

Given,7a−9b=0 or b=79aHence, number of pairs (a, b) can be (9,7); (18, A); (27 ,21); (36,28). Hence, the required probability is 4/39C2=4/741