The total mass of 2 boxes and 3 tanks was 6.1 kg.
The total mass of 5 boxes and 5 tanks was 12 kg.

1. What is the mass of 1 box and 1 tank?
2. What is the mass of 10 tanks?
3. How much less is the mass of 1 tank than 1 box?

(a)
2 boxes + 3 tanks = 6.1 --- (1)
5 boxes + 5 tanks = 12 --- (2)

(2) _{÷ 5}
1 box + 1 tank = 2.4 --- (3)

Mass of 1 box and 1 tank = 2.4 kg

(b)
(3) x 2
2 boxes + 2 tanks = 2 x 2.4
2 boxes + 2 tanks = 4.8 --- (4)

(1) - (4)
(2 boxes + 3 tanks) - (2 boxes + 2 tanks) = 6.1 - 4.8
2 boxes - 2 boxes + 3 tanks - 2 tanks = 1.3

1 tank = 1.3

10 tanks = 1.3 x 10 = 13

Mass of 10 tanks = 13 kg

(c)
Substitute 1 tank = 1.3 into (3).
1 box + 1 tank = 2.4
1 box + 1.3 = 2.4
1 box = 2.4 - 1.3 = 1.1

Mass of 1 box = 1.1 kg

Mass of 1 box less than 1 tank
= 1.3 - 1.1
= 0.2 kg

Answer(s): (a) 2.4 kg; (b) 13 kg; (c) 0.2 kg