To solve this problem, we need to determine the value of x, which represents the booking fee for flying from A to B.
We know that the distance from A to B is 3250 km.
The cost to take an airplane is a booking fee plus $0.10 per kilometer.
We can set up the equation as follows:
Cost to fly from A to B = Booking fee + (Distance from A to B * Cost per kilometer)
Cost to fly from A to B = x + (3250 * 0.10)
Let's simplify and solve for x:
Cost to fly from A to B = x + 325
We are given that the cost to fly from A to B is $425.
Therefore, we have the equation:
425 = x + 325
To isolate x, we subtract 325 from both sides of the equation:
425 - 325 = x + 325 - 325
100 = x
The value of x is 100.
The answer is: 100
Below is a math problem. Provide a detailed, step-by-step solution.

### Problem:
Piravena must make a trip from $A$ to $B,$ then from $B$ to $C,$ then from $C$ to $A.$ Each of these three parts of the trip is made entirely by bus or entirely by airplane. The cities form a right-angled triangle as shown, with $C$ a distance of $3000\text{ km}$ from $A$ and with $B$ a distance of $3250\text{ km}$ from $A.$ To take a bus, it costs Piravena $\$0.15$ per kilometer. To take an airplane, it costs her a X booking fee, plus $\$0.10$ per kilometer. [asy]
pair A, B, C;
C=(0,0);
B=(0,1250);
A=(3000,0);
draw(A--B--C--A);
label("A", A, SE);
label("B", B, NW);
label("C", C, SW);
label("3000 km", (A+C)/2, S);
label("3250 km", (A+B)/2, NE);
draw((0,125)--(125,125)--(125,0));
[/asy]  To begin her trip she flew from $A$ to $B.$ Determine the cost to fly from $A$ to $B. 425. What is the value of unknown variable X?

### Answer:
