Install and Update Solidity(solc) in Mac

You can install and update solc:

brew update
brew upgrade
brew tap ethereum/ethereum
brew install solidity
brew link --overwrite solidity

Errors

If you got the error below, you have to update xcode.

==> Installing solidity from ethereum/ethereum
Error: Your Xcode (9.0) is too outdated.
Please update to Xcode 10.1 (or delete it).
Xcode can be updated from the App Store.