genuine doubt

https://preview.redd.it/cm2s6bdwen0h1.png?width=1098&format=png&auto=webp&s=87995817e154f713cd60f28bc1e978eff3f09c8c

11s2 did anyone solve this, i wasnt getting answer , didnt expect bro to be 0

https://preview.redd.it/rgtlm9t1fn0h1.png?width=1160&format=png&auto=webp&s=3dd97010391828076318ffcef1e79695deca449e

i didnt even understand how 2 is the answer

also how does one solve these questions in a fuckin min