Question 77209
area=(1/2)*16*(base1+base2)
given base1=20
let base2 =x
then 
area=(1/2)*16*(20+x)=224
20+x=(224*2)/16
20+x=28
x=28=20=8
so the other base is 8 m long. 
verification:
area=1/2)*16*(28)=224
ok..good day.. 
(Ps * is used as multiplication symbol to avoid confusion with base x)