tolong no 28 pake cara

(a+b)xt : 2
(6+12) x 4 : 2
18x4 : 2
=36

L.trapesium=1/2*(a+b)*t
=1/2*(12cm+6cm)*4cm
=1/2*18cm*4cm
=1/2*72cm
=36cm2
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