Aylanaga ichki chizilgan $ABCD$ to'rtburchakda qarama-qarshi burchaklar uchun $\angle A = 3x + 10^\circ$ va $\angle C = 2x + 20^\circ$ tengliklar o'rinli. $\angle A$ burchakning daraja o'lchovini toping.
- A. $100^\circ$
- B. $80^\circ$
- C. $30^\circ$
- D. $110^\circ$