write the following intervals in set-builder form:
(i) {: R, -4 < 6}
(ii) {: R, -12 < -10}
(iii) {: R, 0 <7}
(iv) {: R, 3 4}

Let A = {1, 2, {3, 4}, 5}. Which of the following statements are false and why?
(i) {3, 4} ⊂ A 
(ii) {3, 4} ∈ A 
(iii) {{3, 4}} ⊂ A 
(iv) 1 ∈ A 
(v) 1 ⊂ A 
(vi) {1, 2, 5} ⊂A 
(vii) {1, 2, 5} ∈ A
(viii) {1, 2, 3}⊂ A 
(ix) φ ∈ A 
(x) φ ⊂ A
(xi) {φ A 

Write down all the subsets of the following sets
(i) {a} (ii) { a,b} (iii) {1,2,3} (iv)

Write the following intervals in set-builder form:
(i) (-3,0) (ii) [6,12] (iii) (6,12] (iv) [-23,5)

What universal set(s) would you propose for each of the following:
(i) The set of right triangles. (ii) The set of isosceles triangles.