Question

In a group of 70 elderly people , 45 drink tea , 18 drink coffee and 35 drink both tea and coffee. How many people drink tea only?

Answer 1

You have conflicting data, as I will explain at the end

Make a Venn diagram, with two overlapping circles, label them C and T

enter 35 in the intersection.
Since the T circle must contain 45, but you have already 35 entered , the part with only tea must be 45-35 or 10

Check your data for coffee drinkers.
the number of people who drink coffee can't be 18, since you also said that 35 drink both coffee and tea
Everything would work if there were 60 coffee drinkers, with 25 drinking only coffee.