X equals -3. if you need the steps just search up the equation!
The sequence is arithmetic since the common difference that is equal
d=11-15=7-11=-4
a(n) = a1 +(n-1)d
a1=15
=
a(n) = 15+(n-1)-4
Answer:
The value is 
Step-by-step explanation:
From the question we are told that
The number of times is n = 20
The probability of getting three or more heads in a row is
The probability of getting three or more heads in a row or three or more tails in a row is 
Generally given that it is a fair coin , then 
Here P(T) is probability of getting three or more tails in a row
Generally the probability of getting three or more heads in a row and three or more tails in a row is mathematically represented as

=> 
=> 
The key information here is the time he took to run the race - 420 seconds
We know that there are 60 seconds in 1 minute so to find the number of minutes we divide 420 by 60 to get 7.
Murad took 7 minutes to run the race