1. The problem is to simplify the expression $28,4:12$. 2. First, we need to clarify the notation. Assuming the colon ":" means division, the expression is $28.4 \div 12$. 3. The formula for division is $\frac{a}{b}$ where $a$ is the dividend and $b$ is the divisor. 4. Calculate $28.4 \div 12$: $$\frac{28.4}{12}$$ 5. Simplify by dividing numerator and denominator by 4 (to show cancellation): $$\frac{\cancel{28.4}}{\cancel{12}} = \frac{7.1}{3}$$ 6. Now divide $7.1$ by $3$: $$7.1 \div 3 = 2.366\ldots$$ 7. Rounded to three decimal places, the result is $2.367$. Therefore, the simplified value of $28.4 \div 12$ is $2.367$.