14) A ratio of isosceles triangle is 1:1:√2. Since you have m:n:√6, your m and n are both 3(because √6=3*√2)

16) A ration of an equilateral triangle is 1:1:1, and if you divide it into two, it will be 2:1:√3. In the question, you need to know r and s. r=2, and s=√3.

18) I cannot read the question, as the pic is vague.

19)30-60-90 triangle is a half of an equilateral triangle. Thus, you need to use a ratio of 2:1:√3. Then, c is the only option, that will not end up with the ratio below.