Final answer:
To calculate the cost of a 4-line ad, multiply the cost of the additional lines ($1.35 each for 3 lines) with their number and add the cost of the first line ($2.70), resulting in a total cost of $6.75.
Step-by-step explanation:
The cost of running a 4-line ad in a weekly newspaper can be calculated as follows: The first line costs $2.70, and each additional line costs half of that, which is $1.35. Since the ad is 4 lines long, it includes one first line and three additional lines.
- Cost of the first line: $2.70
- Cost of the remaining three lines: 3 lines × $1.35 per line = $4.05
- Total cost of the ad: $2.70 + $4.05 = $6.75