4 tanks and 3 pails can hold 29.6 litres of water.
1 tank and 1 pail can hold 8.5 litres of water.

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

(a)
4 tanks + 3 pails = 29.6 --- (1)
1 tank + 1 pail = 8.5 --- (2)

(2) x 3
1 tank + 1 pail = 8.5
3 tanks + 3 pails = 8.5 x 3
3 tanks + 3 pails = 25.5 --- (3)

(1) - (3)
(4 tanks + 3 pails) - (3 tanks + 3 pails) = 29.6 - 25.5
4 tanks + 3 pails - 3 tanks - 3 pails = 4.1
4 tanks - 3 tanks + 3 pails - 3 pails = 4.1

1 tank = 4.1

Volume of 1 tank = 4.1 ℓ

(b)
Substitute 1 tank = 4.1 into (2).
1 tank + 1 pail = 8.5
4.1 + 1 pail = 8.5

1 pail = 8.5 - 4.1 = 4.4

Volume of 1 pail = 4.4 ℓ

(c)
Volume of 9 pails
= 9 x 4.4
= 39.6 ℓ

(d)
Volume of 3 pails and 4 tanks
= 3 x 4.4 + 4 x 4.1
= 13.2 + 16.4
= 29.6 ℓ

Answer(s): (a) 4.1 ℓ; (b) 4.4 ℓ; (c) 39.6 ℓ; (d) 29.6 ℓ