In math the sum means to add
X+6 > -18+9x
18+6 > 8x
24 > 8x
3 > x

The probability of getting 0 heads in 4 tosses (or equivalently, 4 tails) is

.
So the desired probability is
Answer:
Original Equation: s + 3 1/2 = 8 1/2
Subtract 3/12 from both sides: s + 3 1/2 - 3 1/2 = 8 1/2 - 3 1/2
Simplify: s = 5
So, A is the correct answer.
Let me know if this helps!