Thinking makes us strong

• You give 6 pencils to a person.

$\huge \color{#3D99F6}10 - 6 = \color{#BA33D6}4 ~ \text{pencils}$

• You gained 8 pencils from another person.

$\huge \color{#D61F06}4 + 8 = \boxed{\color{#20A900}12 ~ \text{pencils}}$

• You put 6 pencils in your pocket.

$\huge \color{#EC7300} \text{It doesn't matter, you still have 12 pencils}$

i have 10, i took 8 from another person.so, I should have 18 pencils .but I gave 6 to someone.

so, now i have only $18-6=12$ pencils

$\large 10-6+8=12$ Then you put $6$ pencils in your pocket.So you still have $12$ pencils .