Define the following sets by compression:
a) $$A = \{b,c,d,f,g,h,\ldots,z\}$$ b) $$B = \{a,e,i,o,u\}$$ c) $$C = \{1,2,3,4,5\}$$
See development and solution
Development:
In the first, we notice that the elements of our set are the consonants of the ABC, therefore, we can define the set $$A$$ as $$A =\{\text{consonants of the alphabet}\}$$.
The second are the vowels of the alphabet, so that $$B = \{\text{vowels of the alphabet}\}$$.
And the third are the natural numbers less than or equal to $$5$$, then $$C = \{x\in\mathbb{N} \ | \ x\leq 5 \}$$.
Solution:
a) $$A =\{\text{consonants of the alphabet}\}$$
b) $$B = \{\text{vowels of the alphabet}\}$$
c) $$C = \{x\in\mathbb{N} \ | \ x\leq 5 \}$$