Răspuns :
12 / 21 = ( 12 × 3 ) / ( 21 × 3 ) = 36 / 63
3 / 4 = ( 3 × 3 ) / ( 4 × 3 ) = 9 / 12
8 / 5 = ( 8 × 3 ) / ( 5 × 3 ) = 24 / 15
24 / 25 = ( 24 × 3 ) / ( 25 × 3 ) = 72 / 75
12 / 21 = ( 12 × 3 ) / ( 21 × 3 ) = 36 / 63
3 / 4 = ( 3 × 3 ) / ( 4 × 3 ) = 9 / 12
8 / 5 = ( 8 × 3 ) / ( 5 × 3 ) = 24 / 15
24 / 25 = ( 24 × 3 ) / ( 25 × 3 ) = 72 / 75