7 tanks and 6 containers can hold 48.4 litres of water.
1 tank and 1 container can hold 7.6 litres of water.

1. How many litres of water can 1 tank hold?
2. How many litres of water can 1 container hold?
3. How many litres of water can 4 containers hold?
4. How many litres of water can 6 containers and 7 tanks?

(a)
7 tanks + 6 containers = 48.4 --- (1)
1 tank + 1 container = 7.6 --- (2)

(2) x 6
1 tank + 1 container = 7.6
6 tanks + 6 containers = 7.6 x 6
6 tanks + 6 containers = 45.6 --- (3)

(1) - (3)
(7 tanks + 6 containers) - (6 tanks + 6 containers) = 48.4 - 45.6
7 tanks + 6 containers - 6 tanks - 6 containers = 2.8
7 tanks - 6 tanks + 6 containers - 6 containers = 2.8

1 tank = 2.8

Volume of 1 tank = 2.8 ℓ

(b)
Substitute 1 tank = 2.8 into (2).
1 tank + 1 container = 7.6
2.8 + 1 container = 7.6

1 container = 7.6 - 2.8 = 4.8

Volume of 1 container = 4.8 ℓ

(c)
Volume of 4 containers
= 4 x 4.8
= 19.2 ℓ

(d)
Volume of 6 containers and 7 tanks
= 6 x 4.8 + 7 x 2.8
= 28.8 + 19.6
= 48.4 ℓ

Answer(s): (a) 2.8 ℓ; (b) 4.8 ℓ; (c) 19.2 ℓ; (d) 48.4 ℓ