If the probability of rain ia 0.87, what is the probability of no rain?

Let E be a certain Event.

Let E' be the complement of that event, that is the denial or opposite, of that event.

Some examples:

E: Rolling a 2, from a die      E': rolling 1, 3, 4, 5 or 6

E: Picking red                 E': picking any color except red

E: getting married in January       E': getting married not in January.

Always, P(E)+P(E')=1

Thus if E: "raining", and P(E)=0.87

P(E')=P(not raining)=1-P(E)=1-0.87=0.13

0.13 

4should be the last one n=4