If it decreases at 4% every year, then its value becomes:
100% - 4% = 96% = 96/100 = 0.96
At the end of the 1 year its value becomes: 150*(0.96)
At the end of the 2 years its value becomes: 150*(0.96)*(0.96) = 150*(0.96)²
At the end of the 3 years its value becomes: 150*(0.96)*(0.96)*(0.96) = 150(0.96)³
So similarly at the end of 12 years, its value becomes 150*(0.96)¹²
=50*(0.96)¹² simplify with calculator.
≈ 91.91
Value at the end of 12 years becomes ≈ $91.91
I hope this helps.