用三个变量分别代表不同含义，最后输出一下就可以

#include <iostream>
using namespace std;

int main()
{
    double s;
    cin >> s;
    double x1,x2,x3;
    if (s > 0 && s <= 400) {
        x1 = s * (1 + 0.15);
        x2 = s * 0.15;
        x3 = 0.15 * 100;
    } else if (400.01 <= s && s <= 800) {
        x1 = s * (1 + 0.12);
        x2 = s * 0.12;
        x3 = 0.12 * 100;
    } else if (800.01 <= s && s <= 1200) {
        x1 = s * (1 + 0.1);
        x2 = s * 0.1;
        x3 = 0.1 * 100;
    } else if (1200.01 <= s && s <= 2000) {
        x1 = s * (1 + 0.07);
        x2 = s * 0.07;
        x3 = 0.07 * 100;
    } else {
        x1 = s * (1 + 0.04);
        x2 = s * 0.04;
        x3 = 0.04 * 100;
    }
    printf("Novo salario: %.2lf\n",x1);
    printf("Reajuste ganho: %.2lf\n",x2);
    printf("Em percentual: %.0lf %%\n",x3);
}