3 containers and 2 tanks can hold 13.5 litres of water.
1 container and 1 tank can hold 5.2 litres of water.

1. How many litres of water can 1 container hold?
2. How many litres of water can 1 tank hold?
3. How many litres of water can 8 tanks hold?
4. How many litres of water can 3 tanks and 3 containers?

(a)
3 containers + 2 tanks = 13.5 --- (1)
1 container + 1 tank = 5.2 --- (2)

(2) x 2
1 container + 1 tank = 5.2
2 containers + 2 tanks = 5.2 x 2
2 containers + 2 tanks = 10.4 --- (3)

(1) - (3)
(3 containers + 2 tanks) - (2 containers + 2 tanks) = 13.5 - 10.4
3 containers + 2 tanks - 2 containers - 2 tanks = 3.1
3 containers - 2 containers + 2 tanks - 2 tanks = 3.1

1 container = 3.1

Volume of 1 container = 3.1 ℓ

(b)
Substitute 1 container = 3.1 into (2).
1 container + 1 tank = 5.2
3.1 + 1 tank = 5.2

1 tank = 5.2 - 3.1 = 2.1

Volume of 1 tank = 2.1 ℓ

(c)
Volume of 8 tanks
= 8 x 2.1
= 16.8 ℓ

(d)
Volume of 3 tanks and 3 containers
= 3 x 2.1 + 3 x 3.1
= 6.3 + 9.3
= 15.6 ℓ

Answer(s): (a) 3.1 ℓ; (b) 2.1 ℓ; (c) 16.8 ℓ; (d) 15.6 ℓ