UNIX for Dummies Questions & Answers

#!/bin/bash
echo -n "Enter any two numbers :"
read a
read b
MENU="
Select any one option
1) Addition
2) Substraction
3) Multiplication
4) Division
5) Quit"
clear
$x=0;
while [ $x -ne 5 ]
do
echo "$MENU"
echo ""
echo -n "Please make your choice "
read x
echo ""
case $x in
1) echo $[a+b] ;;
2) echo $[a-b] ;;
3) echo $[a*b] ;;
4) echo `$[a/b]| bc -l `;;
5|q|Q) exit 0 ;;
6) clear
echo "Please choose from the alternatives 1, 2, 3, 4 or 5"
sleep 1 ;;
esac
done
echo ""

math.sh: line 15: =0: command not found
math.sh: line 17: [: -ne: unary operator expected

x=0

"math.sh: line 28: 0: command not found"

"4) echo $[a/b] ;;"

$ a=1
$ b=2
$ echo $[a+b]
3

4) echo `$[a/b]| bc -l `;;

4) echo $[a/b]| bc -l ;;

$x=0;

x=0

echo $a/$b | bc -l