for 11x+7y = 100, after getting a solution (4,8) , how can you surely say that for getting a next solution x has to be decreased and y has to be increased…?It can be a reverse too..?
No, because we observed the pattern above. And think about it, if the total has to remain the same, then if one part is increased the other must be decreased…
CAT-holics 
11x+7y = 100
7y = 100 – 11x
y = 14 – x – ( 4x -2)/7, since y is integer, so (4x-2) should be divisible by 7… dis approach works well for such cases…
for 11x+7y = 100, after getting a solution (4,8) , how can you surely say that for getting a next solution x has to be decreased and y has to be increased…?It can be a reverse too..?
No, because we observed the pattern above. And think about it, if the total has to remain the same, then if one part is increased the other must be decreased…
regards
J