1. Stating the problem: We need to find the value of the missing numerator in the fraction $\frac{4}{?}$ such that it is equivalent to $\frac{28}{70}$. 2. Understanding equivalent fractions: Two fractions $\frac{a}{b}$ and $\frac{c}{d}$ are equivalent if $a \times d = b \times c$. 3. Set up the equation for equivalence: $$4 \times 70 = ? \times 28$$ 4. Calculate the left side: $$280 = ? \times 28$$ 5. Solve for the unknown numerator by dividing both sides by 28: $$? = \frac{280}{28}$$ 6. Simplify the fraction by canceling common factors: $$? = \frac{\cancel{280}}{\cancel{28}} = 10$$ 7. Final answer: The missing numerator is 10, so the equivalent fraction is $\frac{10}{4}$ which simplifies to $\frac{28}{70}$ when scaled appropriately.