In the given circuit the value of | I _ 1 + I _ 3 I _ 2 | is:

Potential distribution at each point in the circuit is shown in above diagram.

Since, both $10Ω$ resistors are maintained at same potential difference, so current will be same, thus, using Ohm's law, ${I}_{1} = {I}_{2} = \dfrac{20 - 10}{10} = 1A$

Now, current ${I}_{3} = \dfrac{10}{10} = 1A$

Hence, the value of \left|\dfrac{{I}_{1} + {I}_{3}}{{I}_{2}}\right| = \dfrac{1 + 1}{1} = 2.