CODE EXAMPLE FOR SHELL

assigning variables bash

gamma_t=540
gamma_new="$(($gamma_t-360))" # get gamma_new by $gamma_t-360 

num2="$(($num1+num2))" 

$((expression))      # you can do expressions like this

a=5

yourname_$(($a-1)) 	#dynamic varibales. 
#will give
yourname_4