1. **State the problem:** Solve for $y$ in the equation $\frac{4.5}{y} = \frac{12.5}{4}$.\n\n2. **Write the formula and explain:** This is a proportion equation where two ratios are equal. To solve for $y$, we can cross-multiply: $4.5 \times 4 = 12.5 \times y$.\n\n3. **Cross-multiply:** $$4.5 \times 4 = 12.5 \times y$$\n\n4. **Calculate the left side:** $$18 = 12.5 \times y$$\n\n5. **Isolate $y$ by dividing both sides by 12.5:** $$y = \frac{18}{12.5}$$\n\n6. **Show cancellation step:** $$y = \frac{\cancel{18}}{\cancel{12.5}}$$ (no common factors to cancel, so just rewriting)\n\n7. **Simplify the fraction:** $$y = 1.44$$\n\n**Final answer:** $y = 1.44$