fast jawab kwan........

Misal:
A = Aji
B = Budi

A = B - 6 disubstitusi ke
A + B = 36
B - 6 + B = 36
2B = 36 + 6
2B = 42
B = 21
A = B - 6
A = 21 - 6
A = 15

B : A = 21 : 15 = 7 : 5

Jadi jawabannya ada di pilihan 3 yaitu 7 : 5.