code is too long

a = 4;
b = input ('2+2=?    ')
if b == a
    'ok'
else
    b = input ('retry  ')
    if b == a
        'ok'
    else
        b = input ('retry  ')
        if b == a
            'ok'
        else 'NOK'
        end
    end
end

Answer 1

[Image Analyst]

I think you want

a = 4;
b = 0;
while b ~= a
  b = input ('2+2=?    ');
  if b == a
    break;
  end
  fprintf('Incorrect.  Try again.\n');
end
fprintf('Correct.\n');

[Image Analyst]

If you want to limit it to three tries, add a counter:

a = 4;
b = 0;
counter = 1;
while b ~= a && counter <= 3
  b = input ('2+2=?    ');
  if b == a
    break;
  end
  fprintf('Incorrect.  Try again.\n');
  counter = counter + 1;
end
if counter <= 3
  fprintf('Correct.\n');
end

Answer 2

[Nicolò]

Yes, but I would like to repeat this code up to three times if the number entered is incorrect

[Image Analyst]

This is not an answer to your question. It should have been a comment to my answer so I'll put the response there.

[Nicolò]

thanks