The * operator multiplies two numbers: int product = 4 * 5; stores 20. You must use the asterisk; writing 4x or 4(5) causes a compilation error. Multiplication has higher precedence than addition.
In int result = 2 + 3 * 4;, C++ multiplies first: 3 * 4 = 12, then adds 2 to get 14. Multiplying large integers can overflow. int big = 50000 * 50000; exceeds the typical int range and wraps to a negative number.
Use long long for large products.