Answer
You would have to raise the temperature by $17.65^{\circ} C$ to $\approx 18^{\circ} C$.
Work Step by Step
The copper wire will remain essentially unchanged in length and cross-sectional area. Resistivity needs to increase by 12%.
$ρ = ρ_{0} [1 + α (T - T_{0})]$
Plug 12% increase in.
$ρ = ρ_{0} [1 + 0.12]$
$ \Delta T = T - T_{0}$
Set the portion inside the brackets equal to each other.
$1 + α \Delta T = 1 + 0.12$
$\Delta T = \frac{0.12}{α}$
From the textbook for copper, $α = 0.0068 /^{\circ} C$
$\Delta T = \frac{0.12}{0.0068 /^{\circ} C}$
$\Delta T = 17.65 ^{\circ} C$
You would have to raise the temperature by $17.65^{\circ} C$.