Angle BCA = 180 - 100
angle BCA = 80
Isosceles triangle ABC has two congruent angles, A and B
2x + 80 = 180
2x = 100
Angles A and B = 50 or y and z = 50
I think lines AB and DE are supposed to be parallel, so angles y and x are consecutive interior angles (supplementary)
x = 180 - 50 = 130
Final answer is...... positive 15/8
For two ratios to form a proportion they have to be equal.
To see if two ratios are equal we express them in their simplest form.
In this case we notice that in the first ratio both numbers are multiples of five, then:

In the second case we notice that both numbers are multiples of 2, then:

Since both ratios can be simplified to the same final ratio, they form a proportion.
A) Volume = l * w* h --> V = 7 * 5 * 4 --> V = 140 units³
B) 140 units³: Prism B has the same length, width, and height as A, just rotated.
C) As long as the tree numbers' product is 140 units³, it works.
Prism C: 140 * 1 * 1
Prism D: 14 * 2 * 5
170.
Area = b x h
17 x 10 = 170