Respostas

2014-04-05T23:18:47-03:00
Se b/4 = c/2 => b = 4c/2 => b = 2c, substituindo em: 

b+c = 90 => 2c + c = 90 => 3c = 90 => c = 90/3 => c = 30.

Se c = 30, logo b = 2c => b = 2.30 => b = 60
2014-04-05T23:22:00-03:00
b + c = 90

b = c
4    2

b+c = b
4+2    4

90 = b
 6     4

6b = 360
  b = 60

b + c = 90
c = 90 - 60
c = 30