Jack rolls a number cube twice. What is the probability that the sum of the 2 rolls is less than 8 given that the first roll is a 4?

one over two

one over six

one over three

five over six

If the first roll is a 4, the possibilities to add less than 8 are that the second cube roll is 1, 2 or 3.

These are 3 different events out of 6 possilbe ones, which is 3 / 6 = 1 / 2; i. e. half of times.

Then the answer is the first option: 1 / 2