Two probability equations for counter counts

Core stretch

A bag contains \(x\) red and \(y\) yellow counters. The probability of red is \(\frac{3}{8}\). One counter is selected at random.

1. Form an equation connecting \(x,y\).[2]
2. Four red counters are added and the probability of yellow becomes \(\frac{1}{2}\).
   1. Form a second equation.[2]
   2. Find \(x,y\).[2]