Respostas

2014-08-04T17:15:37-03:00
123,5       100 %
x              10 %

123,5*10/100= 12,35  % 
2014-08-04T17:16:08-03:00
123,5----------100
x-----------------10
100x=1235
x=1235/100
x=12,35
espero ter ajudado