Дроби к общему знаменателю: a) 3/7 = ? / 14 и 1/2 = ? /14 б) 5/6 = ? / 12 и 3/4 = ? /12 в) 2/5 = ? /15 и 7/15 = ? /15г) 5/6 = ? и 5/8 = ? д) 7/9 = ? и 1/6 = ? е) 5/4 = ? и 3/5 = ?

3/7=6/14 и 1/2=7/14
5/6=10/12 и 3/4=9/12
2/5=6/15 и 7/15=7/15
5/6=20/24 и 5/8=15/24
7/9=14/18 и 1/6=3/18
5/4=25/20 и 3/5=12/20

a) 3/7 = ?/ 14 и 1/2 = ?/14
3/7 = 3*2/ 14 и 1/2 = 1*7/14
3/7 = 6/ 14 и 1/2 = 7/14

 б) 5/6 = ?/ 12 и 3/4 = ?/12
5/6 = 5*2/ 12 и 3/4 = 3*3/12 
5/6 = 10/ 12 и 3/4 = 9/12 

в) 2/5 = ?/15 и 7/15 =  ?/15
2/5 =2*3/15 и 7/15 =  1*7/15
2/5 = 6/15 и 7/15 =  7/15

г) 5/6 = ? и 5/8 = ?
5/6 = 40/48 и 5/8 =30/48

д) 7/9 = ? и 1/6 = ?
7/9 = 42/54 и 1/6 =9/54

 е) 5/4 = ? и 3/5 = ? 
5/4 = 25/20 и 3/5 = 12/20