Question 377826
Imagine this:
If you were to lay the two given sides flat so they form a single contiguous straight line, this line would be 12 (5+7) units long. Now you could not possibly make a triangle by adding a third side of 12 units, it would have to be shorter than 12 in order to make a triangle and, since you are dealing with integral sides, the third side could be no longer than 11 units, making the maximum perimeter 7+5+11 = 23 units.