1 is x=13.5
2 is x=-260
3 is x=38
4 is x=-37^38
i think this is correct
Start by multiplying b to both sides of the equation to get rid of the fraction. Now you have: Ub = ak.
To isolate a, divide both sides of the equation by k. 
= a is the final answer.
<h3>
Answer: Choice A) 0.20</h3>
===================================================
Explanation:
Let's say there are 1000 students. The students must take math, science or they can take both simultaneously.
- 65% of them are in math. So there are 0.65*1000 = 650 math students.
- 43% are in science, leading to 0.43*1000 = 430 science students.
- 13% are in both so we have 0.13*1000 = 130 students who are in both.
Now onto the sentence that says "Suppose a high school student who is enrolled in a math class is selected at random"
This means we only focus on the 650 math students and ignore the 1000-650 = 350 students who aren't in math.
Of those 650 math students, 130 are also in science (since 130 are in both classes).
The probability we're after is therefore 130/650 = 0.20
