Andy has some counters.

15% of the counters are red.

of the counters are blue.

The rest of the counters are yellow.

There are 27 yellow counters.

How many blue counters are there?

Let total counters are 100. Then red are = 15*100/100=15. Let A are the no. of blue counters. As yellow are 27. So red+Blue+yellow=100. ie 15+A+27=100. So A=100.15-27=58. ie Blue are 58%