C I'm using the calculator and the other ones don't make sense
The pictures confused me, can you explain them please?
F(x)= -4x+9
Multiply f*x
xF=9+4x
Solve for X: -4x+xF=9+4x-4x=0
Combine like terms: -4x+4x=0
-4x+xF=9+0= 9
-9+-4x +xF = 0.
Since she has seven key the probability that the first one will open the door is

if it takes three attempts to open the door,the probability is

if the three attempts would not work
then the probability that the fourth attempt will open the door is

hope this helps
the answer was c
hope that helps your!!!!!