1. The user states the value is 21 13/80, which is a mixed number. 2. To understand or convert this, recall that a mixed number consists of a whole number and a fraction. 3. The mixed number 21 13/80 means $21 + \frac{13}{80}$. 4. To convert this to an improper fraction, use the formula: $$\text{improper fraction} = \text{whole number} \times \text{denominator} + \text{numerator}$$ 5. Calculate: $$21 \times 80 + 13 = 1680 + 13 = 1693$$ 6. So, the improper fraction is $$\frac{1693}{80}$$. 7. This confirms the mixed number 21 13/80 is equivalent to $$\frac{1693}{80}$$. 8. If you want to convert it to a decimal, divide numerator by denominator: $$\frac{1693}{80} = 21.1625$$. 9. Therefore, 21 13/80 is exactly $$\frac{1693}{80}$$ or approximately 21.1625 in decimal form.