Which sport contains Popular formations include the 4-2 , 6-2 , and 5-1 systems ?
Examples get quite complicated quickly , here are small examples: " n " = " n " ( by rule 1 ) " p → q " = " pq " ( by rule 2 ) Thus 3 → 4 = 34 = 81 1 → ( " any arrowed expression " ) = 1 since the entire expression eventually reduces to 1number = 1.