It's elementary theorem that angles on the circumference of the circle 'looking' at the same arc of that circle are themselves equal. (the proof is a bit long but if necessary I can try to write it, try this Circumferential Angle Is Half Corresponding Central Angle ; the theorem works for any circumferential angle.)

BAL is 'looking' at the arc AB but is degenerated.

When you know this you can find the second part easily just observing the angles ABC and the angle at A 'looking' at arc AC.

Sorry if my English was bad.