Understanding Uninitialized Variable on I am a String!

Tell us what’s happening:

Your code so far

// Initialize these three variables
var a;
var b;
var c;

// Do not change code below this line

a = a + 1;
b = b + 5;
c = c + " String!";

var a = 6;
var b = 15; 
var c = 'I am a string!';

Your browser information:

Your Browser User Agent is: Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.84 Safari/537.36.

Link to the challenge:
https://www.freecodecamp.org/challenges/understanding-uninitialized-variables