How can someone add if adding means that someone subtracts?

THANKS TO MY PATRONS!
Natalie Woolf
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Thanks to DiV4 for the 21 gif!
@DiV_twt on Twitter

SONG USED: Scatman John - Scatman's World

MEME USED: What's 9 plus 10

BACKGROUND VIDEOS USED:
1:    • The Best View of the Grand Canyon  
2:    • Video  
3:    • Clouds Free STOCK FOOTAGE  
4:    • Driving Between New York City Skyscra...  
5:    • Road Trip Copyright Free Video Footag...  
6:    • City Life | Drone Video - Free HD Vid...  
7:    • Video  
8:    • FREE Chicago Stock VIDEOS! On Pexels  
9:    • 4K 60 fps Sand Dunes Stock Footage (F...  
10:    • FLYING A DRONE AT SUNSET (FREE FOOTAGE)  
11:    • Houston In 4K HD DJI Drone  (Free Sto...  

EXTRA VIDEOS USED:
Thanos dancing:    • DANCING THANOS    GREEN SCREEN  
Flying math equations:    • Math Equations Chalk screen green  
Blinking math equations:    • Green Screen Mathematics  Effects [4K]  
Decoding numbers:    • Decoding Numbers Animation (green scr...  

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you stupid