Use the idea of binary linear equation: get X points for answering a question correctly, and get Y points for not answering or answering a question incorrectly.
There are four conditions that can be listed as equations, and it is enough to choose two of them, such as
{ 19x-y=94
18x-2y=88
Simultaneous solution, x=5, y= 1.
② Impossible.
It is also verified by equation thought.
Set the answer to question A correctly, and don't answer or answer the question B incorrectly.
{5A-B=65
A+B=20
The simultaneous solution A is not an integer, so this situation is impossible.