The change in length of the wire due to change in temperature

$=\mathrm{\alpha }LT=1.2\times {10}^{-5}\times 3\times \left(-170-30\right)$

$=-7.2\times {10}^{-3}\mathrm{m}$

The change in the length of the wire due to the stretching force

$=\frac{F L}{A Y}= \frac{10\times 10\times 3}{0.75\times {10}^{-6}\times 2\times {10}^{11}}$

$=2\times {10}^{-3} \mathrm{m}$

The total change in the length of the wire

$=-7.2\times {10}^{-3}+2\times {10}^{-3}$

$=-5.2\times {10}^{-3} \mathrm{m}=-5.2 \mathrm{mm}$

The negative sign indicates contraction of the wire