Hello,Please help me!This is my math work
Find the unknown value of a

Answer:
104°
Step-by-step explanation:
The sum of interior angles in a pentagon is 540°
107° + 121° + 3a° = 540°
3a° + 228° = 540°
3a° = 540° - 228°
3a° = 312°
a° = 104°