The first x coordinate is given by 0 and the second one is given as j. So the length of the base is j. (Sometimes in math they give letters rather than numbers. And since you know it is an isosceles then the other vertex should be at x-coordinate half j or j/2.
There are total of 5 digits, of which we arrange 3 of them.
Therefore using permutations we can find total possible 3-number combinations.
5P3 = 5*4*3 = 60
To be greater than 600 means first digit must be 6. (1 possibility)
A number is even only if last digit is even, 2 or 4. (2 possibilities)
The 2nd digit then can only be 3,5, (2 or 4). (3 possibilities)
The total possible even 3-digit numbers greater than 600 is product of each digit's possibilities.
---> 1*3*2 = 6
Therefore probability is 6/60 = 1/10.
The answer is A because 25 percent is equivalent to .25
310 / 75-5 = 4.42 or 4.4 hours. Let me know if you have any other questions.