80,000. it easy rally we learnt this in 2nd grade
Supplementary angles
x+20+5x+10=180
6x+30=180
6x=150
x=25
12 ft by 15 ft is 180 square feet. 180 square feet is 20 square yards. So take 20 multiplied by 25$ and thats how much money you have to spend to carpet Fred's room. so basically 500$
Because the spacing is in inches, the total length of the string is 28 * 12 = 336 inches long
subtract the distance to the first light: 336 - 16 = 320 inches left
the spacing is 4 inches so now you would divide the length by the spacing to get the quantity of lights:
320 / 4 = 80 lights