I've been stuck on this for a little while now and i think i've been going round in circles for what is probably a very easy answer.

I'm trying to do a simple equation involving variables in a bash script. Below is the basics of my more complex bash script. Could anyone help me with this please? 

On top of this i would also like to complete the final equation with the below (1 step at a time). I saw that I would probably be required to use bc to handle the non integer, but i didnt get that far!

```
#!/bin/bash
a=20
b=25
echo $( ("$a" + "$b") )

```

Error

```
bash -x test1
+ a=$'20\r'
+ b=$'25\r'
++ $'20\r' + $'25\r'
test1: line 4: $'20\r': command not found
+ echo $'\r'

```

Final equation (not much different i know)

```
 #!/bin/bash
    a=20
    b=25
    echo $( ("$a" + "$b" / 100) )

```