Question

Consider the following sets.

U = {all triangles}

E = {x|x ∈ U and x is equilateral}
I = {x|x ∈ U and x is isosceles}
S = {x|x ∈ U and x is scalene}
A = {x|x ∈ U and x is acute}
O = {x|x ∈ U and x is obtuse}
R = {x|x ∈ U and x is right}

Which is a subset of I?

E
S
A
R

Answer 1

E.

Every equilateral triangle has (at least) two equal sides, so E ⊆ I. The others (scalene, acute, right) include triangles that are not isosceles.