9 pails and 8 tanks can hold 37.9 litres of water.
1 pail and 1 tank can hold 4.4 litres of water.

1. How many litres of water can 1 pail hold?
2. How many litres of water can 1 tank hold?
3. How many litres of water can 9 tanks hold?
4. How many litres of water can 9 tanks and 9 pails?

(a)
9 pails + 8 tanks = 37.9 --- (1)
1 pail + 1 tank = 4.4 --- (2)

(2) x 8
1 pail + 1 tank = 4.4
8 pails + 8 tanks = 4.4 x 8
8 pails + 8 tanks = 35.2 --- (3)

(1) - (3)
(9 pails + 8 tanks) - (8 pails + 8 tanks) = 37.9 - 35.2
9 pails + 8 tanks - 8 pails - 8 tanks = 2.7
9 pails - 8 pails + 8 tanks - 8 tanks = 2.7

1 pail = 2.7

Volume of 1 pail = 2.7 ℓ

(b)
Substitute 1 pail = 2.7 into (2).
1 pail + 1 tank = 4.4
2.7 + 1 tank = 4.4

1 tank = 4.4 - 2.7 = 1.7

Volume of 1 tank = 1.7 ℓ

(c)
Volume of 9 tanks
= 9 x 1.7
= 15.3 ℓ

(d)
Volume of 9 tanks and 9 pails
= 9 x 1.7 + 9 x 2.7
= 15.3 + 24.3
= 39.6 ℓ

Answer(s): (a) 2.7 ℓ; (b) 1.7 ℓ; (c) 15.3 ℓ; (d) 39.6 ℓ