alrighty, so this is a standard rate and multiplication problem. How do we know? Well, because there's a steady rate of 2/10 per day, and for 3 days so:
2/10 x 3 = 6/10
6/10 can be simplified:
6/10 ÷ 2 = 3/5
So Daniel eats 3/5 yogurt over the course of 3 days