Number of ribbons that can be cut = 6 ÷ 1/2
Number of ribbons that can be cut = 6 x 2/1
Number of ribbons that can be cut = 12
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Answer: 12 1/2 foot pieces can be cut from 6 feet ribbon
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We add up all those numbers (excluding 30) and divide by the number of numbers (9). This results in 78.8 (round up to 79).
79-74 = 5. So the mean has increased by 5 points. (C)
Since both of the numbers have a variable which is x ready to be multiplied, there is no expression leading to the variable therefore you will add normally but you will need to put the missing variable which needs to be multiplied. So overall you can just add and once you get your variable you can be abe to multiply and get your final answer.
Hope this helps