Answer:
Tom should buy the plants from Kirsty as 59.75 < 63.
Step-by-step explanation:
Tom is going to buy 25 plants to make a hedge.
Cost of buying plants from Kirsty:  2.39 x 25 = £59.75
Long multiplication:
2.39
x 25
- - - -
11.95
47.80
- - - - -
59.75
Cost of buying plants from hedge world:
10% of £52.50 = 5.25
so 20% of £52.50 = 5.25 x 2 = 10.50
total cost = 52.50 + 10.50 = £63
So Tom should buy the plants from Kirsty as 59.75 < 63.