The 4 should be rolled 15 times, for every 90 rolls.
First you want to create the two into fractions-> 1/6 = x/90 The 1 in 1/6 is the chance of 4 showing in a dice roll. The x in x/90 is the chance how many 4’s there should be in 90 rolls.
You can turn that into 6x = 90 by cross multiplying the two fractions. Then turn that into x = 15.
