It is 9
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What you would do is simply plug in 8 where y is and solve.
5(8)=3478-3c -Times 5 by 8
40=3478-3c -Add 3c to the opposite side of the equal sign
40+3c=3478 -Subtract 40 from the opposite side of the equal sign
3c=3438 -Divide equation by 3
c=1146
Hope this helps! :)
Answer:
AB // CD and AD // BC, then ABCD is a parallelogram
Step-by-step explanation:
Step 2: Show AD // BC
A = (-3 , 3) and D = (0 , 0)
Find the slope of AD

B = (2 , 5) and C = (5 , 2)

The slope of AD = the slope of BC
So AD // BC because they have the same slope
Step 3:
Each two opposite sides are parallel in quadrilateral ABCD
So the quadrilateral is a parallelogram
Last one is correct
good luckkkkkkk