Answer :
Step-by-step explanation:
Let's break it down step by step:
1. 20% of the number = 0.2 × x (where x is the number)
2. 25% of that result = 0.25 × (0.2 × x) = 0.05x
3. 50% of that result = 0.5 × (0.05x) = 0.025x
We know that 0.025x = 21, so:
x = 21 / 0.025
x = 840
So, the number is 840.