So permiter=masure of all sides added together so sides are(3x+2), (2x+5), and (4x) so (3x+2)+(2x+5)+(4x) use associative property a+(b+c)=(a+b)+c so
(3x+2)+(2x+5)+(4x)=3x+2+2x+5+4x group like terms becasue can move numbers around (3x+2x+4x)+(2+5) add like terms (9x)+(7) 9x+7 he will use 9x+7=perimiter