minimize question with lagrange

Question

Q. Minimize $$ \mathrm{f} = {1 \over 2} \left(x_{1} + x_{2} + x_{3}\right) \ \mbox{subject to}\ \left\{\begin{array}{rcl} {\displaystyle\mathrm{g}_{1}\left(X\right)} & {\displaystyle =} & {\displaystyle x_{1} - x_{2} = 0} \\[1mm] {\displaystyle \mathrm{g}_{2}\left(X\right)} & {\displaystyle =} & {\displaystyle x_{1} + x_{2} + x_{3} - 1 = 0} \end{array}\right. $$ Is this problem can solve with Lagrange multiplier ??. It's my first time learning, so I'm not good at it. Please someone help me !.