Answer
$2HCl(aq)+ Ba(OH)_{2}(aq)\ -->\ 2H_{2}O(l)+ BaCl_{2}(aq)$
Work Step by Step
The acid and base neutralize each other to form $H_{2}O$. To balance the equation, add a 2 to the $HCl$ as there are two $Cl^{-}$ ions in the products. Then add a 2 to the $H_{2}O$ as there are two $H^{+}$ and $OH{-}$ ions in the reactions forming two $H_{2}O$ molecules.