Let

be a probability that i-th light fails, where i=1,2,3. Then,

is the probability that i-th light remain bright.
<span>If the lights fail independently of each other, the probability that a string of lights will remain bright for two years is:
</span>

.
-3 is the slope.
Explanation:
We would use the slope formula for this.
Slope formula: y2-y1/x2-x1
1-(-8)/-1-2
9/-3
-3
1. 5+4
2. 7+2
The answer is 9.
I hope I helped! :)
Answer: 64
Step-by-step explanation: