All students in each grade because it should not be limited based on gender or if they like social studies or not.
SOLUTION
Given the question in the image, the following are the solution steps to answer the question.
STEP 1: State the number of outcomes possible for three tossing of a coin
Since a coin has two possible outcomes and is tossed three times, the total outcomes will be:

STEP 2: Find the number of sample spaces for the three tosses
STEP 3: Get the outcomes of the events for which the second toss is tails
Hence, the answers are given as:
Sample Space:

The event that the second toss is tails:
0.9 = -4.7 - 0.6z
0.9 + 4.7 = -0.6z
5.6 = -0.6z
z = 5.6 ÷ -0.6
z = -9.33