Im really confused!!​

What are the exclude value of mn+3m

What is the value of n in the equation -1/2(2n+4)+6=-9+4(2n+1)

Scenario: a rectangular plot of ground is 5 meters longer than it is wide. its area is 20,000 square meters. question: what equation will you find the dimensions? note: let w represent the width. options: w(w+5)=20,000 w^2=20,000+5 (w(w+5))/2=20,000 w+2(w+5)=20,000