Answer:
cost of knife = £5.52
Step-by-step explanation:
Assume:
Cost of Knife = a
Cost of Spoon = b
a = 3b ----------------------(1)
12a + 9b = £82.80 -------(2)
Substitute equation (1) in equation (2)
12 * (3b) + 9b = £82.80
36b + 9b = £82.80
45b = £82.80
b = £1.84
Therefore, cost of knife = a = 3 * £1.84 = £5.52
