Inversion of operators
Addition, subtraction
Addition is the inverse of subtraction: $$(x - a) + a = x$$ $$ (6 - 2) + 2 = 6
$$
Subtraction is the inverse of addition: $$(x + a) - a = x$$ $$ (3 + 2) - 2 = 3$$
Division is the inverse of multiplication $$ \frac{a \cdot x}{a} = x$$ $$ \frac{6 \cdot 3}{6} = 3 $$
Multiplication is the inverse of division $$ a \cdot \frac{x}{a} = x$$
$$ 2 \cdot \frac{8}{2} = 8 $$