Question 972966
t for correct answers; add 3.
f for wrong answers; subtract 2.


Twenty questions, score of 0.
{{{system(t+f=20,3t-2f=0)}}}.
You should analyze and formulate that system, and therefore understand that system.  Solving for t and f is something you already  learned.  Suggestion:  Start with Elimination method, using first equation as {{{2t+2f=40}}}.