500
Caer (TO FALL), Leer (TO READ), Incluir (TO INCLUDE), and Creer (TO BELIEVE) involve this type of spelling change in the Irregular Preterit form of ELLOS/ELLAS/USTEDES
What is an I------>Y spelling change.
caYeron: They Fell
leYeron: They Read
incluyeron: They Included
creyeron: They Believed