The answer is 45°
By determining the angles of triangle ACB (A=30°, B=45°, C=105° (total of 180°)) and knowing that angle 1 correlates to angle 4 ((1)°=(4)°), we can find angle 1, which is 45°, equal to angle 4.
2 3/4a=19 1/4
÷2 3/4 ÷2 3/4
a=1/7
Answer: -3
Step-by-step explanation: Explanation is below
:) Hopes this helps!