tolong yaa kak............... 26. AD = 15 cm.

..
25)
EA(EB) = ED(EC)
18(3) = ED (9)
ED = 18(3) / 9
ED = 6

26.
AF  = AB (AD) / BD)
AF = 20(15)/(25)
AF = 12

BF² = AB² - AF²
BF² = 20² - 12² = 400 - 144 = 256
BF = 16

FD = BD - BF
FD = 25 - 16
FD = 9

FD² = AF x FE
9² = 12 x FE
FE = 81/12 = 6, 75

AE = AF + FE
AE = 12 + 6,75
AE = 18,75

Luas trapesium ABED  = luas ΔADE + Luas ΔABE
Luas ABED =  1/2 AE . FD  + 1/2 .AB. AD
Luas ABED = 1/2  ( AE .FD + AB. AD)
Lua ABED = 1/2 (18,75 x 9  + 20 x 15)
Luas ABED = 1/2 (168.75 + 300) = 1/2 (468,75)
Luas ABED = 234, 375  atau 234, 4 cm²

27. ABCD adalah  layang layang
AB = AD = 6
BC = CD = 8
AC² = AD² + CD² = 6² +8² = 100
AC = 10

BD  = 2 DE
BD = 2 (AD x CD/ AC)
BD  = 2 (6x 8)/10
BD  = 96/10
BD = 9,6 cm
DE tegak lurus A