A jar contains only​ pennies, nickels,​ dimes, and quarters. There are 23 ​pennies, 22 ​dimes, and 20 quarters. The rest of the coins are nickels. There are 79 coins in all. How many of the coins are not​ nickels? If n represents the number of nickels in the​ jar, what equation could you use to find​ n?