# How does this addition work (13+7=1130)?

I found this problem on 9gag and I have no idea how to solve it.

Here is the question:

$13+7=1130$

$88+9=47$

$32+28=2530$

$10+999=1149$

$444+77=61$

$55+111=56$

$21+0=1221$

$7+22=39$

$33+5=38$

$123+45=???$

The puzzle says to think outside the box.

Here is the image:

• Well, the ones' digits are all correct, so the answer probably ends in 8... – Joe Z. Jul 12 '15 at 19:34
• If possible I think it might be wise to source/link where you go this puzzle from if you just copied it. – Mark N Jul 13 '15 at 14:45
• Sure, 9gag.com/gag/azVrZRj – Jorge Fernández Jul 13 '15 at 14:48
• Looking at your latest edit, is the answer supposed to have three digits? – mmking Jul 13 '15 at 14:58
• Not sure if it's relevant, but in the original the 1s and the kerning around them are odd. $21+0=1221$ almost looks like $21+0=\lvert 22 \rvert$ to me. – Edward Jul 13 '15 at 16:25