Answer
280°C
Work Step by Step
$ρ_{Al} [1+α(T-20°C)] = ρ_{W}$ divide both sides by $ρ_{Al}$
$1+α(T-20°C)= \frac{ρ_{W}}{ρ_{Al}}$ subtract 1 from both sides
$α(T-20°C)= \frac{ρ_{W}-ρ_{Al}}{ρ_{Al}}$ divide out $\alpha$
$T-20°C= \frac{ρ_{W}-ρ_{Al}}{ρ_{Al}{α}}$ add $20°C$
$T= \frac{ρ_{W}-ρ_{Al}}{ρ_{Al}{α}} +20°C = 279.485°C \approx 280°C$