My question is do I need another mikrotik at Site A to connect to Site C or can I use the existing Mikrotik at Site A connecting to Site B to also connect to Site C? Thanks! Sorry about the handwriting and quick drawing. 
the mikrotiks already in place at site a and b are cloud core routers.
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Am I not explaining something right? is my network diagram that bad to not understand? i’ve not worked with mikrotik devices and came into this configuration already setup, they want to add another location to the link and share the existing internet and the voip system at site A. Just need to know if I need to buy 2 mikrotiks or just one for the new site. Help please
At first sight, it looks big and scary, that’s probably why nobody took a bait so far. Looking at it a little closer, it seems that it’s just five subnets and you already have some of them connected (bridged?) between Site A and Site B. So if you manage to get those other two subnets, that are not already there, to mikrotik at site A, you should probably be able to connect Site A and Site C the same way as Site B is already connected. So only one new device could be enough. But don’t blame me if it doesn’t work, there might be some problems that are not apparent from your drawing.
my only thought would be how would it know to send 192.168.20x.xxx out site b or site c interface or it would just send them out both. some traffic would be site c only so that isnt a major concern of it going to site b, but voip is shared along with some other things and of course internet.
You already have same subnets on site A and B, so I assume it’s somehow bridged together. So some hosts in each given subnet are on site A and some on B. If this works, it will also work if you extend the whole thing by including site C. Of course, if you share any additional details about how exactly it’s currently configured, it can only help. Also what those sites are, if it’s few buildings next to each other, or if they are each on the other end of the world, etc.
It’s same city linked by fiber they do it this way to share the Internet and voip along with servers on site a
And any info about current config used by those MikroTik routers?
No don’t have the login info will have to redo the configs