7 is 35% out of 20, when you divide 7 by 20, you get 0.35 which is 35%.
To find<span> the width, multiply the </span>length<span> that you have been given by 2, and subtract the result from the perimeter. You now have the total </span>length<span> for the remaining 2 </span>sides<span>. This number divided by 2 is the width.</span>
80 - 2p
You use the distributive property