The total weight of a mini-helicopter and a toy car is 3.3 kg. The total weight of a mini-helicopter and a toy plane is 5.4 kg. If the total weight of a toy plane and a toy car is 6.33 kg, find the total weight of the mini-helicopter, the toy car and the toy plane.
Let 1 mini-helicopter be 1 M.
Let 1 toy car be 1 T.
Let 1 toy plane be 1 P.

1 M + 1 T = 3.3 --- (1)
1 M + 1 P = 5.4 --- (2)
1 P + 1 T = 6.33 --- (3)

(1) + (2) + (3)
1 M + 1 T + 1 M + 1 P + 1 P + 1 T = 3.3 + 5.4 + 6.33
2 M + 2 T + 2 P = 15.03
2(1 M + 1 T + 1 P) = 15.03 

1 M + 1 T + 1 P = 15.03 ÷ 2
1 M + 1 T + 1 P = 7.515

 Total weight of the mini-helicopter, the toy car and the toy plane = 7.515 kg

Answer(s): 7.515 kg