The total weight of a jigsaw puzzle and a water gun is 3.4 kg. The total weight of a jigsaw puzzle and a toy train is 4.6 kg. If the total weight of a toy train and a water gun is 5.17 kg, find the total weight of the jigsaw puzzle, the water gun and the toy train.
Let 1 jigsaw puzzle be 1 J.
Let 1 water gun be 1 W.
Let 1 toy train be 1 T.

1 J + 1 W = 3.4 --- (1)
1 J + 1 T = 4.6 --- (2)
1 T + 1 W = 5.17 --- (3)

(1) + (2) + (3)
1 J + 1 W + 1 J + 1 T + 1 T + 1 W = 3.4 + 4.6 + 5.17
2 J + 2 W + 2 T = 13.17
2(1 J + 1 W + 1 T) = 13.17 

1 J + 1 W + 1 T = 13.17 ÷ 2
1 J + 1 W + 1 T = 6.585

 Total weight of the jigsaw puzzle, the water gun and the toy train = 6.585 kg

Answer(s): 6.585 kg