I got 2 arrays in my program, the first one is numbers and the second one is not, while trying to compare them, I am getting this error :

```
./P5.4.sh: line 48: [: /: integer expression expected
./P5.4.sh: line 48: [: *: integer expression expected
./P5.4.sh: line 36: [[: -: syntax error: operand expected (error token is "-")
```

this is line 36 :

```
if [[ (( "${formula[i-1]}" -ge "0" && "${formula[i-1]}" -le "9$
(( "${formula[i+1]}" -ge "0" && "${formula[i+1]}" -le "9" )) ]]
```

and this is line 48 :

```
if [ "${formula[i+1]}" -ge "0" ] && [ "${formula[i+1]}" -le "9" ]
```