Can someone please solve this for me? GIVE STEP BY STEP EXPLAINATION
WILL GIVE BRAINLIEST

There are 11 counters in a bag.
6 of these counters are green.
5 of these counters are red.
Some more red counters are put into the bag.
A counter is then taken at random from the bag.
The probability that the counter is red is
3/5
How many red counters were put into the bag?