Appendix A - Section A.1 - Introduction to Functions - A.1 Problem Set - Page 488: 59

See below.

Plugging in $t=3$ we get: $V(3)=150\cdot2^{3/3}=300$, this means that the painting is worth $\$300$ in 3 years. Plugging in $t=6$ we get: $V(6)=150\cdot2^{6/3}=600$, this means that the painting is worth $\$600$ in 6 years.