Im going to go out on a limb and say its one.
3.14 x 8^2 = 200.96 (divided by) 2 = 100.48
1/2 (8 x 12) = 48 x 2 = 96
100.48 + 96 = 196.48
A = 196.48
Alright, we just need to reverse some operations done unto 43. Subtract the 15 from her collection.
43 - 15 = 28.
Sold half? Times half.
28 * 2 = 56
Make sure it works:
56 - 28 = 28. 28 + 15 = 43.
She had 56 cards to start with.
Look at the pictures (examples)
m∠1 = m∠6 → answer: none
m∠2 = m∠3 → answer: none
m∠2 = m∠C → answer: none