Question 167483
let W=Width , L=length , P=perimeter  

P=2L+2W
L=2W-5

take L's and perimeter value and plug it into Perimeter equation.
1.

80=2(2W-5)+2W
80=4W-10+2W
90=6W--->{{{W=15}}} width
{{{L=2(15)-5=25}}} length

2.if there are 80 sq ft in order to get the number of square yards you must
  divide by 9---->80/9=8.89 sq yds  so 8.89(12)={{{106.68}}}

3. amount of wall space is perimeter of the room which is 80*8=640 

if paint covers 200 sqft the number of gallons needed would be 640/200
which equals 3.2 meaning we have to buy 4 gallons to cover the walls
...4*14.99/gal={{{59.96}}}
4.area of ceiling is 25*15=375 sq ft  so if one package covers 50 sq ft
..375/50=7.5 so it will take 8 packages of tiles to cover ceiling
....8*39.99={{{319.92}}}
5. so with the misc supplies of {{{28}}} we have{{{28+319.92+59.96+106.68=514.56-dollars}}}cost to do family room