Final answer:
To convert the ratio 21:84 to a decimal, divide 21 by 84 which results in 0.25.
Step-by-step explanation:
To convert a ratio to a decimal, divide the first number by the second number of the ratio. In this case, divide 21 by 84. 21 ÷ 84 = 0.25.
Learn more about Converting a ratio to a decimal