[ferget]

Код:

#include <iostream>
int main()
{
float a,b;
char op;
float res;

std::cout<<"Enter expression: ";
std::cin>>a>>op>>b;

if (op == '-')
res =a-b;
else if (op == '+')
res = a+b;
else if ((op == '/')&&(b!=0))
res =a/b;
else if (op == '*')
res = a*b;
else 
{
	if (b==0)
	{std::cout<<"na 0 delit nelzya"<<std::endl;
	return 0;
	}else
	{
	std::cout<<"bad operation"<<std::endl;
	return 0;
	}
}
std::cout<<"resultat: "<<res<<std::endl;
return 0;
}

или код LilLoco,