#1**-3 **

7/10 drink tea, so 7/10 * 400 = 280 drink tea, 120 dont, 20% drink at least 3 cups a day, so 280*0.2 = 56, and the rest don't.

56/400 = 28/200 = 14/100 = 7/50.

If you don't understnad anything feel free to ask.

hugomimihu Apr 21, 2020

#3**-3 **

The question states that "20% of the people who drink tea drink at least 3 cups a day". 20% in decimal form is 0.2, or if you use fractions, 20/100 = 2/10 = 1/5. We then multiply this with the number of people drinking tea, 280, and get 280*0.2, or 280 * 1/5. We multiply because the 0.2 is a part of the whole, so when we multiply by that, it gives us the value.

hugomimihu
Apr 21, 2020