Solve {l}{a_{1}+a_{2}+a_{3}=4}{a_{1}+a_{3}=2}{a=a_{2}}{text{Solvefor}btext{where}}{b=a}

$$\left. \begin{array} { l } { a_{1} + a_{2} + a_{3} = 4 }\\ { a_{1} + a_{3} = 2 }\\ { a = a_{2} }\\ { \text{Solve for } b \text{ where} } \\ { b = a } \end{array} \right.$$

Solve for a_1, a_2, a_3, a, b

$$b=2$$