As we know that;
Total number of possible outcomes $=20$ ($5$ red, $8$ white & $7$ black}
(i) Let E = event of drawing a red or white ball
So, No. of favorable outcomes $=13(5$ red $+8$ white)
Therefore Probability, P(E) = Number of favorable outcomes/ Total number of outcomes
P(E) = 13/20
(ii) Now Let E = event of getting a black ball
No. of favorable outcomes $=7$($7$ black balls)
Thus, Probability, $P(E)=$ Number of favorable outcomes/ Total number of outcomes
P(E)$=7/20$
$\overset{\scriptscriptstyle\rightharpoonup}{E}=$Event of not getting black ball
$P(\overset{\scriptscriptstyle\rightharpoonup}{E})=1-P(E)$
$P(\overset{\scriptscriptstyle\rightharpoonup}{E})=1-\frac{7}{20}$
$P(\overset{\scriptscriptstyle\rightharpoonup}{E})=\frac{13}{20}$