Problem Solving (PS) | When a certain tree was first planted, it was 4 feet tall

Initial =4 ft
year1 = 4ft +x
year 2= 4ft +2x
year 3= 4ft +3x (pattern)
year 4= 4ft + 4x
year 5 = 4ft +5x
year 6= 4ft +6x

year 6 = year 4 + 1/5(year 4)
4ft +6x = 4ft+4x + 1/5(4ft +4x)
2x= (4ft +4x)/5
10x = 4ft+ 4x
6x=4ft
x=(4/6)ft = (2/3)ft
answer d

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