Me it’s super easy. based on the given information, which conjecture is invalid? given: a rectangle has a perimeter of 24 inches

The conjecture that would be incorrect is the third conjecture "The rectangle has a length of 12." The perimeter is the sum of all the sides, and if 2 of the sides are 12, that means that half of the perimeter is already 24, which means that the other 2 sides would have to be 0, which is impossible.

if you was gonna solve for a, a is a   < -12