tolong bantu saya mengerjakannya

P-10000/12000-10000 = Q-100/80-100
P-10000/2000 = Q-100/-20
Kali silang
-20P+200000 = 2000Q-200000
-20P=2000Q-400000
Ruas kanan dan ruas kiri dibagi -20
Pd = -100Q+20000