17. \( \frac{72 \mathrm{lb}}{1 \mathrm{ft}^{3}}=\frac{x \mathrm{~T}}{1 \mathrm{yd}^{3}} \)

To convert the density from pounds per cubic foot (lb/ft³) to tons per cubic yard (T/yd³), we need to apply some conversion factors. We know that there are 3 feet in a yard, so 1 yd³ = \(3^3\) ft³ = 27 ft³. Additionally, there are 2000 lb in a ton (US tons). First, we convert 72 lb/ft³ to lb/yd³: \[ 72 \mathrm{~lb/ft}^3 \times 27 \mathrm{~ft}^3/\mathrm{~yd}^3 = 1944 \mathrm{~lb/yd}^3. \] Next, we convert pounds to tons: \[ \frac{1944 \mathrm{~lb}}{1 \mathrm{~yd}^3} \times \frac{1 \mathrm{~T}}{2000 \mathrm{~lb}} = 0.972 \mathrm{~T/yd}^3. \] So, the final answer is approximately \(x \approx 0.972 \mathrm{~T/yd}^3\).