Question: I'm new to LaTeX and I have a question about the LaTeX code (which I have to do for my essay), for the inner product of vectors on an exponential\*,how can I fix the problem that the two vektors k and x have their vectors taht are not parallel . *The vector of k is much higher that the vector in x* ( I use the command \overrightarrow for the vector, and I have also use the \displaystyle for a sum that exist in the same equation).

How can I fix that?

Thanks cheers :)

Answer: 
Actually, X11 is not erased but moved to /opt/X11. 

So, the simplest solution would probably be to manually add the symbolic link from /usr/X11 to /opt/X11: 

```
sudo ln -s /opt/X11 /usr/X11

```
Same problem after installing OSX Catalina ...

But now, you need to make a link like this: 

```
sudo ln -s /opt/X11 /private/var/select/X11

```

(The link `/usr/X11` points to `/private/var/select/X11` and can't be modified.)