X = 5a + 3
X = 7b + 4
Y = 5c + 3
Y = 7d + 4
X-Y = 5a - 5c + 3 - 3
X-Y = 7b - 7d + 4 - 4
X-Y = 5(a-c)
X-Y = 7(b-d)
X-Y must be a multiple of 5 and 7 .. So Option E...
Alternatively
Values can be 3,8,13,18,23,28,33,38,43
Values can also be 4,11,18,25,32,39,46
Common is 18 - Now 18 is a number that that has both 3 remainder when divided by 5 and 4 remainder when divided by 7.... So the next number which gives us the same when we will had 7 x 5 =35 in it.... And then again thr next will be when we add 35 again...
Suppose Y is 18
X is 35+18=53
X-Y = 35
You pick any two numbers it will always give a multiple of 35...
X = 5a + 3
X = 7b + 4
Y = 5c + 3
Y = 7d + 4
X-Y = 5a - 5c + 3 - 3
X-Y = 7b - 7d + 4 - 4
X-Y = 5(a-c)
X-Y = 7(b-d)
X-Y must be a multiple of 5 and 7 .. So Option E...
Alternatively
Values can be 3,8,13,18,23,28,33,38,43
Values can also be 4,11,18,25,32,39,46
Common is 18 - Now 18 is a number that that has both 3 remainder when divided by 5 and 4 remainder when divided by 7.... So the next number which gives us the same when we will had 7 x 5 =35 in it.... And then again thr next will be when we add 35 again...
Suppose Y is 18
X is 35+18=53
X-Y = 35
You pick any two numbers it will always give a multiple of 35...