A steel wire 1.2 mm across and 2.4 m long hangs from a hook…

Step 1. Area. $A = \pi(0.60 \times 10^{-3}\ \text{m})^2 = 1.131 \times 10^{-6}\ \text{m}^2$.

Step 2. Force constant. $k = 2.0 \times 10^{11}\ \text{Pa} \times \dfrac{1.131 \times 10^{-6}\ \text{m}^2}{2.4\ \text{m}} = 9.42 \times 10^{4}\ \text{N/m}$.

Step 3. Stretch. $\Delta L = \dfrac{F}{k} = \dfrac{150\ \text{N}}{9.42 \times 10^{4}\ \text{N/m}} = 1.59 \times 10^{-3}\ \text{m}$.