What is the equation of the blue line ?

Can someone check if i did this right since i really want to make sure it’s correct. if you do you so much

Louis wants to carpet the rectangular floor of his basement.the basement has an area of 864 square feet.the width of the basement is 2/3 it's length. what is the length of louis's basement

Find the nonpermissible replacement for binthis expression.b2/5b +5