Respostas

2013-09-27T22:03:52-03:00
A/15 = 28/20
20a=420
a=420/20
a=21
------------

12/15 = b/20
15b=240
b=240/15
b=16
4 4 4
2013-09-27T22:12:11-03:00
 \frac{a}{28}  \frac{12}{b}  \frac{15}{20}

12 x 20 = b x 15 ------ b= 16

a x 20 = 28 x 15 ------ a= 21
3 4 3