The SafeMath.sol library provides basic addition, subtraction, multiplication, division, and modulo mathematical calculation functions that can be used in your contract.
The OpenZeppelin contract present at Chapter09/openzeppelin-solidity/contracts/math/SafeMath.sol is defined as follows:
library SafeMath { function mul(uint256 a, uint256 b) internal pure returns (uint256) { if (a == 0) { return 0; } uint256 c = a * b; require(c / a == b); return c; } function div(uint256 a, uint256 b) internal pure returns (uint256) { require(b > 0); uint256 c = a / b; return c; } function sub(uint256 a, uint256 b) internal pure returns (uint256) { require(b <= a); uint256 c = a - b; return c; } function add(
