How to subtract a value?

[gregm]

I've setup snmp on a raspberry pi and would like to graph CPU usage.

I'm managed to get the OID for idle CPU which is 99 on most cases. Is there a way to say 100 - idle value and plot this?

[gregm]

Anyone have any ideas?

[Atsushi]

I think it is better to create calculated items.

https://www.zabbix.com/documentation/3.0/manual/config/items/itemtypes/calculated