int a = Convert.ToInt32(Console.ReadLine());
bool b = a <= 17;
bool c = a >= 61;
bool d = b && c;
Console.WriteLine("结果是{0} false为青年,true不是青年",d);
bool isYoung = a>=18 && a<= 60;
int res = 3 + 2 * 4;
console.writeline(res);
运算符有优先级