ducks and ducklings stumper?

Question

Three big ducks went out one day
with two ducklings behind
14 kilograms was their weight
when all five were combined

add one duck and one duckling
and their weight increased
19 kilograms was the total
of the seven with webbed feet

if all ducklings have one weight,
and ducks all have other
the you should find the total weight
of three-one child,two mothers

can you also explain please?

Answer 1

Let D = weight of a duck
Let d = weight of duckling
First statement says:
(1) 3D + 2d = 14
Second statement says:
(2) (3D + 2d) +D + d = 19
(2) 4D + 3d = 19
Multiply equation (1) by 4:
(1) 12D + 8d = 56
Multiply equation (2) by 3:
(2)12D + 9d = 57
Subtract equation (1) form equation (2):
(2) 12D + 9d = 57
-(1) 12D + 8d = 56
d = 1
(1) 3D + 2d = 14
3D + 2(1) = 14
3D = 12
D = 4
One child and two mothers:
1d + 2D = 1 + 2(4) = 9kilograms