Look are the tests and follow those instead (6, 15 etc)
And pls let me know here if that worked. You can then open a new GitHub issue to get this fixed.
Bugs can be reported as GitHub Issues. Whenever reporting a bug, please check first that there isn’t already an issue for it and provide as much detail as possible.
I tried that, and return success. Maybe it’s a glitch
// Only change code below this line
var a = 5;
var b = 10;
var c = "I am a";
// Only change code above this line
a = a + 1;
b = b + 5;
c = c + " String!";
Try resetting the step with the Restart button and force the browser to refresh with CTRL-F5 and then paste the 3 lines of code from your original post.