Step-by-step explanation:
[tex]\angle{a} = 56°[/tex] using the definition of vertical angles
The sum of the interior angles of a triangle is 180 so
[tex]\angle{a} + \angle{b} + 90 = 180[/tex]
[tex]\Rightarrow 56° + \angle{b} + 90° = 180°[/tex]
or
[tex]\angle{b} = 34°[/tex]
