To evaluate this expression properly, we must follow order of operations (PEMDAS) rules. Here, that means doing exponentiation first, followed by mult. and div., followed by addition and subtraction.
2−4÷2+2^3 becomes 2−4÷2+8 after exponentiation.
2−4÷2+8 becomes 2-2+8 after division.
2-2+8 = 8
Your final value for this expression is 8.