How do I find percent change, so confused, please help.

During a bike challenge riders have to collect various colored ribbons each 1/2 mile they collect a red ribbon each eighth mile they collect a green ribbon and each quarter mile they collect a blue ribbion wich colors of ribion will be collected at the 3/4 markrer

Can someone check if i did this right since i really want to make sure it’s correct. if you do you so much

Cody was 165cm tall on the first day of school this year, which was 10% taller than he was on the first day of school last year.