## Algebra 1: Common Core (15th Edition)

The missing length is $9x-1$.
The sum of the two given side lengths is $2x+5+5x-1=\quad$.....gather like terms. $=2x+5x+5-1$ $=7x+4$ To find the third side, we subtract the sum of the given two sides from the perimeter. $(16x+3)-(7x+4)=\qquad.$...remove parentheses. $=16x+3-7x-4=\qquad$ .....gather like terms. $=16x-7x+3-4$ $=9x-1$