Final answer:
To convert the mixed number 21/5 to a decimal, convert the fraction 1/5 to 0.2 and add it to the whole number 2, resulting in 2.2.
Step-by-step explanation:
The question asks to rewrite the mixed number 21/5 as a decimal. To do this, you need to convert the fraction part of the mixed number to a decimal. The fraction 1/5 is equal to 0.2 when converted to a decimal. Therefore, we add this decimal to the whole number part of the mixed number. The whole number 2 remains unchanged, so adding 2 and 0.2 gives us the decimal form of the mixed number, which is 2.2.