Shell script create a name for function in Android

i don't know what the right title for this question but i have a problem like this:

i have a file inside a folder, the name is test.txt and have a value 6
i open the terminal and use su command to get root access (just in case), then i try this script

tek="/a/test.txt"
if [ "$tek" -le "8" ]; then
  echo " 6 <= 8 "
else
  echo "nice"
fi

and there is an error sush: /a/test.txt: unexpected '/' tmn
i try another way like this tek="a/test.txt" and i get an error sush: a/test.txt: zero divisor tmn
can someone tell me what is wrong with my script?

i do this all in Android device

if there is someone know what is the right title for this question please change it, i'll be so grateful