The trick to solving this problem is to know and remember that the sum of all the interior angles of a triangle is always 180 degrees.
Thus, (6x+1) + (5x-17) + (9x-24) = 180.
20x = -40, so x = -2 (answer)
I think the percent change would be 25%
Perfect squares are n² where n is a whole number
whole numbers are like 0,1,2,3,4,5,6, etc
no decimal or fractions
we can do that be looking at the perfect squares we know
2²=4
3²=9
4²=16
5²=25
6²=36
7²=49
8²=64
etc
so we see 47 is between 6² and 7²
therefor, for n²=47, n is between 6 and 7 and is therfore not a whole number
that makes 47 not a perfect square