5 positive integers are arranged in ascending order, as follows: 1,9, 9, 10, X
The mean and the median are equal.
Find X.

x = 16

Step-by-step explanation:

Since the numbers are in ascending order, x is the number with the highest value here.

From the arrangement, we can see that the median (the middle number) is the third number which is 9

The mean is the sum of the numbers divided by their count. So we set up the mean and equate to the median

We have this as;

(1 + 9 + 9 + 10 + x)/5 = 9

29 + x = 5(9)

29 + x = 45

x = 45-29

x = 16

3. parallelogram

step-by-step explanation:

we turn each of our sides into direction vectors

ab=b-a=(3 - 7, 1 - 0) = (-4, 1)

bc=c-b=(1,6)

cd=d-c=(4,-1)

da=a-d=(-1,-6)

we see how the opposite sides have negated direction vectors; this is characteristic of a parallelogram.   we have congruent sides ab=cd and bc=da with unequal lengths because 1^2+6^2 is different from (-4)^2+1^2.   so it's not a square or a rhombus.  

we check the dot product of direction vectors of adjacent sides.   we have

ab dot bc = -4(1) + 1(6) = 2

that's not zero so the sides are not perpendicular.   we've ruled out rectangle.

the direction vectors indicate two pairs of congruent parallel sides, so we choose parallelogram over trapezoid.