# Basic JavaScript - Compound Assignment With Augmented Addition

Tell us what’s happening:
Describe your issue in detail here.
my run test button is not working at all nor the ctrl+enter and I had b += 9 before and somehow it was flipped then I had it this way
let a = 3;

let b = 17;

let c = 12;

// Only change code below this line

15 += a = 12;

26 += b = 9;

19 += c = 7;
can someone please help and I also went to the next assignment and it is doing the same thing

``````let a = 3;
let b = 17;
let c = 12;

// Only change code below this line
15 = a += 12;
26 = 9 += b;
19 = c += 7;
``````

User Agent is: `Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/107.0.0.0 Safari/537.36`

Challenge: Basic JavaScript - Compound Assignment With Augmented Addition

Did you see the error message in the console?

``````SyntaxError: unknown: Invalid left-hand side in assignment expression. (6:0)

4 |
5 | // Only change code below this line
> 6 | 15 = a += 12;
| ^
7 | 26 = 9 += b;
8 | 19 = c += 7;
``````

You cannot put a constant on the left side of an assignment expression. The number 15 will always be 15, but a line starting with `15 = ` tells the computer to change 15 to equal some value on the right side, which is impossible, so the whole program will crash.

Your assignment expressions should always start with a variable, because only the value of a variable can vary (hence the name).

If you have a variable `a` with a value of 10, and you want to make it equal 15 via addition, you can enter `a = a + 5;` or `a += 5;` . The line `a = a + 12;` adds 12 to the value of `a` and assigns the new value to `a`. How can you simplify that line using the `+=` operator?

``````let a = 3;
let b = 17;
let c = 12;

// Only change code below this line
a = a + 12;
b = 9 + b;
c = c + 7;

console.log("a == "+a);
console.log("b == "+b);
console.log("c == "+c);
``````

i got ty so much much appreciated

This topic was automatically closed 182 days after the last reply. New replies are no longer allowed.