1.1.a ) pvq&¬r without parenthesis, there is an ambiguity on which operator applies to which pair.
1.1.b) ¬(p&q)&r or (¬pv¬q)&r
1.2.a)  not changing v for & or & for v when using Demorgans.
2.1) Refering to “x” instead of “students”,
 NOT using the word “either” to distinguish windows and iphone,
Saying all the students use both windows and iphone.
3.1) Misinterpreting the question, trying to solve ExEyEz instead,
Trying to solve AyAzEx instead,
Forgetting that the real numbers include the irrational numbers,
Not solving in terms of Y, solving for X.
3.1) Saying x=0 proves it false,
Misinterpreting the question trying to solve ExEyEz or AzAyEx,
Saying z=0 doesn’t exist,
Repeating the question saying “ False, there doesn’t exist an x for every y…” without giving a proper justification.
4.1) Incomplete table with less columns or rows,
Wrong values for implication operator,
Not knowing which columns are the ones that prove the equality.
4.2) Using truth tables to confirm the equality,
Going in circles to prove the equality,
Associating &s with ORs without using the proper rules,
Using double negation when it is unnecessary,
Not saying if they are equal or not from what they did.