Tes TPA, silahkan dicoba, pake cara

ng : nd = (50-40) : (40-35)
ng : nd = 10 : 5
ng : nd = 2 : 1

Misal :
x = Banyak guru
y = Banyak dokter

((x) (35) + (y) (50)) / (x + y) = 40
35x + 50y = 40x + 40 y
50y - 40y = 40x - 35x
10y = 5x
2y = x
2 : 1

Jadi jawabannya B. 2 : 1