Question 370500
We notice that 2xEqu1 - Equ2 (*) gives the weight of : 2 Ducks and 1 duckling
 
(6-4)D + (4-3)d = 2D + d = 2*77 - 107 = 140 + 14 - 107 = 33 + 14 = 47 kg
 
 
from 3m-4n = 2*(2m-3n) => m = -2n, hence the multiplier are 2, -1 for eqn 1 and 2 resp.