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<html><body><h2>JavaScript Variables</h2><p>Remove the comment (at the beginning of the lines) to test each case:</p><p id="demo"></p><script>let x = 5;//x = 5 + 7; // x.valueOf() is 12, typeof x is a number//x = 5 + "7"; // x.valueOf() is 57, typeof x is a string//x = "5" + 7; // x.valueOf() is 57, typeof x is a string//x = 5 - 7; // x.valueOf() is -2, typeof x is a number//x = 5 - "7"; // x.valueOf() is -2, typeof x is a number//x = "5" - 7; // x.valueOf() is -2, typeof x is a number//x = 5 - "x"; // x.valueOf() is NaN, typeof x is a numberdocument.getElementById("demo").innerHTML = x.valueOf() + " " + typeof x;</script></body></html>