Answer:
part 1:
see in the picture, E is the centre of the kite
1) AC = 2.EC = 40
2) CD = sqrt( ED² + EC² ) = sqrt(21² + 20²) = 29
3) ABE = 90⁰ - 51⁰ = 39⁰
4) BCE = BAE = 51⁰
part 2:
we have:
3x + 7 = (3x - 1 + 8x)/ 2
<=> 3x + 7 = 5.5x - 0.5
<=> 2.5x = 7.5
<=> x = 3
5) with x = 3 => UV = 3.3 - 1 = 9 - 1 = 8
6) XY = 3.3 + 7 = 9 + 7 = 16
7) TW = 8.3 = 24
9) the width of the base is x (x > 0)
we have:
28.5 = (x + 25)/2
<=> x + 25 = 57
<=> x = 32