The total weight of a water gun and a rubber ball is 3.5 kg. The total weight of a water gun and a toy house is 5.1 kg. If the total weight of a toy house and a rubber ball is 5.86 kg, find the total weight of the water gun, the rubber ball and the toy house.
Let 1 water gun be 1 W.
Let 1 rubber ball be 1 R.
Let 1 toy house be 1 H.

1 W + 1 R = 3.5 --- (1)
1 W + 1 H = 5.1 --- (2)
1 H + 1 R = 5.86 --- (3)

(1) + (2) + (3)
1 W + 1 R + 1 W + 1 H + 1 H + 1 R = 3.5 + 5.1 + 5.86
2 W + 2 R + 2 H = 14.46
2(1 W + 1 R + 1 H) = 14.46 

1 W + 1 R + 1 H = 14.46 ÷ 2
1 W + 1 R + 1 H = 7.23

 Total weight of the water gun, the rubber ball and the toy house = 7.23 kg

Answer(s): 7.23 kg