Well you should just have to add 7 to 12.
Answer:
2√2
Step-by-step explanation:
< C = 180-15-45 = 120°
AC/sin 45° = AB/sin 120°
AC = 2√3 × sin 45° / sin 120°
= 2√3 × ½√2 / ½√3
= 2√2
20