Numeros enteros

(+21) + (−13) = +8 , (+17) + (+26) = +43
(−41) + (+19) = −22 , (−33) + (−28) = −61
(+10) − (−5) = (+10) + (+5) = +15
(−7) − (+6) = (−7) + (−6) = −13
(−4) − (−8) = (−4) + (+8) = + 4
(+2) − (+9) = (+2) + (−9) = −7