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Work Shown:
x = number of light bulbs
3.40x = total cost to buy x light bulbs, cost is in pounds
3.40x = 30
x = 30/(3.40)
x = 8.823529 approximately
Rounding down, we get 8
Note that,
Therefore, the highest number of bulbs that can be bought is 8.
The change given will be 30-27.20 = 2.80 pounds