ParserError: Expected ',' but got 'payable' admin.transfer(address payable(this).balance); ^-----^

I have write a small smart contract. however there is problem. please see below full code

pragma solidity ^0.5.16;

import "./x.sol";

contract xSale {
address admin;
x public tokenContract;
uint256 public tokenPrice;
uint256 public tokensSold;

event Sell(address _buyer, uint256 _amount);

constructor (x _tokenContract, uint256 _tokenPrice) public {
    admin = msg.sender;
    tokenContract = _tokenContract;
    tokenPrice = _tokenPrice;
}

function multiply(uint x, uint y) internal pure returns (uint z) {
    require(y == 0 || (z = x * y) / y == x);
}

function buyTokens(uint256 _numberOfTokens) public payable {
    require(msg.value == multiply(_numberOfTokens, tokenPrice));
    require(tokenContract.balanceOf(address(this)) >= _numberOfTokens);
    require(tokenContract.transfer(msg.sender, _numberOfTokens));

    tokensSold += _numberOfTokens;

    emit Sell(msg.sender, _numberOfTokens);
}

function endSale() public {
    require(msg.sender == admin);
    require(tokenContract.transfer(admin, tokenContract.balanceOf(address(this))));

    // UPDATE: Let's not destroy the contract here
    // Just transfer the balance to the admin
    
    admin.transfer(address payable(this).balance);
    }
}

getting error
xSale.sol:40:32: ParserError: Expected ‘,’ but got ‘payable’
admin.transfer(address payable(this).balance);
^—–^