When doing this problem, I had to do -6 x 3 and x/3 x 3. This should cancel out the 3 in x/3, leaving you with just x. -6 x 3 is less or equal to -18. To check, I converted -18/3 into a whole number, which gave me -6. This is true to the original inequality. Hope this helped!
The value at the end of the year is 100% - 20% = 0.80 of the value at the beginning of the year. After 4 years of multiplying by this factor, the value is $17,500·0.80⁴ = $7,168
