I'm assuming that you meant 4x+1=3x?
Subtracting 4x, we get 1=-x. Multiplying by -1, we get x=-1 as the solution.
First, we already have the perimeter and the sides that we need to find the 5th sides. Next, add all available sides that we have: 5+5+4+4=18. Finally, we need to subtract 27 to 18 to get the final answer is 9 for the 5 the side. Hope you get it.
First: find area of the entire door
15*6=90
then find area of the brown spot:
9*1=9
finally: subtract
90-9=81
No because 0.6363.... <0.75