Sometimes you might need to figure out your tomcat version from within the folder where you run tomcat from. The below command will help you get the details.
java -cp lib/catalina.jar org.apache.catalina.util.ServerInfo
/usr/share/tomcat7$ java -cp lib/catalina.jar org.apache.catalina.util.ServerInfo
Server version: Apache Tomcat/7.0.81
Server built: Aug 11 2017 10:21:27 UTC
Server number: 7.0.81.0
OS Name: Linux
OS Version: 3.13.0-95-generic
Architecture: amd64
JVM Version: 1.7.0_75-b13
JVM Vendor: Oracle Corporation