The picture may say something..!!

$Let\quad P(A)\quad be\quad the\quad probability\quad of\quad getting\quad red\quad cards\quad out\quad of\quad the\quad deck\quad ,\\ Let\quad P(B)\quad be\quad the\quad probability\quad of\quad getting\quad kings\quad out\quad of\quad the\quad deck\\ and\quad Let\quad P(A+B)\quad be\quad the\quad probability\quad of\quad getting\quad a\quad king\quad or\quad red\quad card\\ \\ P(A)\quad =\quad \frac { 26 }{ 52 } \quad \\ \qquad \qquad \qquad \qquad \qquad \qquad \quad \quad \quad \quad \quad \quad \quad P(A\quad \cap \quad B)\quad =\quad P(A)\quad .\quad P(B)\\ \qquad \qquad \qquad \qquad \qquad \qquad \qquad \quad \quad \therefore \quad P(A\quad \cap \quad B)\quad =\quad \frac { 2 }{ 52 } \\ P(B)\quad =\quad \frac { 4 }{ 52 } \\ \\ P(A+B)\quad =\quad P(A)\quad +\quad P(B)\quad -\quad P(A\quad \cap \quad B)\\ \qquad \qquad \quad =\quad \frac { 26 }{ 52 } \quad +\quad \frac { 4 }{ 52 } \quad -\quad \frac { 2 }{ 52 } \\ \qquad \qquad \quad =\quad \frac { 26\quad +\quad 4\quad -\quad 2 }{ 52 } \\ \qquad \qquad \quad =\quad \frac { 28 }{ 52 } \\ \therefore \quad P(A+B)\quad =\quad \frac { 7 }{ 13 } \quad [Answer]\\$

Event $(A)$ Red card $=26$

Event $(B)$ King cards $=4$

$(A \cup B)=2$

$P(A \cup B)=\dfrac{26+4-2}{52}=\dfrac{28}{52}=\boxed{\frac{7}{13}}$

out of 52 cards there are 26 cards of red color i.e. probability is 26/52 out of 52 cards there are 4 cards of kings i.e. probability is 4/52 now there are 2 king cards which are red in color i.e.probability is 2/52 ACCORDING TO ADDITION THEOREM P(A OR B)==P(A) +P(B) - P(A AND B) i.e. =====26/52 + 4/52 - 2/52 == 28/52==7/13

Red cards are 26. Kings that aren't Red are two. So the probability we are looking for is 28/56=7/13.