day1.js

    // Declare second integer, double, and String variables.
    var j=12;
    var d1 = 4.0;
    var s1 = "is the best place to learn and practice coding!"
    // Read and save an integer, double, and String to your variables.
    var a = i+j;
    var b = (d+d1).toFixed(1);
    var c = s+s1;
    // Print the sum of both integer variables on a new line.
    console.log(a);
    // Print the sum of the double variables on a new line.
    console.log(b);
    // Concatenate and print the String variables on a new line
    // The 's' variable above should be printed first.
    console.log(c);

Are you reading from the input or just hardcoding values??