Answers and explanations:
87. The domain of added functions includes the restrictions of both. So the range of the added function in this question is [-4, 3]
88. When finding the domain of a divided function we do the same as adding, but with an extra rule: g can't equal zero. So for this question the domain is (-4, 3)
89. To graph f + g you add the y-values for each x-value. I added a picture to help explain this one!
Answer: the answer is 180 
Step-by-step explanation:
Area of a rectangle multiply length times base. 15 x 12 = 180. Hope this helps!
For the function 5x, the range is the value of f(x) which is five times the x and the domain is the value of x which can be the ratio of f(x) and 5. For the second function which is g(x) = 5, the range is 5 all through out the graph while the domain is infinity.
How to find the x intercept of 3y=2x-6: (when y is 0)
3(0) = 2x - 6
0 = 2x - 6
+6 + 6
-------------------------
6 = 2x
------ -----
2 2
x = 3
How to find the y intercept of 3y=2x-6: (when x is 0)
3y = 2(0) - 6
y = 0 - 6
3y = -6
------ -----
3 3
y = -2
D. The exclusion is important because we cannot divide by zero. Apart from that we are simply looking at a function.