When 2 dice 1 red, and 1 green are rolled, there at 36 outcomes. If both dice are fair the outcomes are equally likely. Let E be the event that the sum of the numbers rolled is 7. What is the probability of 7 ?

First you have to determine how many ways are there to make a 7.

They are: 1 & 6, 6 & 1, 2 & 5, 5 & 2, 3 & 4, 4 & 3. The fist number is for the red dice and the second number is for the green dice.

Now take the total number of ways a seven can be made and divide it by 36 total possible outcomes to get your answer.