a) 1/5=4/20 <=> 1*20=4*5 <=> 20=20 Adevarat
b) 2/11=4/22 <=> 2*22=11*4 <=> 44=44 Adevarat
c) 0/9=6/9 <=> 0*9=6*9 <=> 0=54 Fals
d) 9/5=36/20 <=> 9*20=5*36 <=> 180=180 Adevarat
e) 6/7=54/56 <=> 6*56=7*54 <=> 336=378 Fals
f) 12/16=3/4 <=> 12*4=16*3 <=> 48=48 Adevarat