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10.5, since 35 is between 30 and 40 ((30+40)/2), the mistakes that correspond with them are 9 and 12, the number in between them is 10.5 (9+12=21, 21/2 is 10.5)
Answer:
its negative
Step-by-step explanation:
The width is 42 inches. If you add 42+42+30+30, it equals 144. (l+l+w+w)