First part:

Ok, for this you need to know that ranges from -1 to 1. You are given that the minimum value of y is 4 and the maximum value of y is 12. Since the sine function is the only value of the function that is going to be changing, this is a relatively easy problem to solve. When the sine is at its least, the function will be at its least. So when the sine is -1, the function is 4. Similarly, when the sine is at its greatest, the function will be at its greatest. So when the sine is 1, the function is 12. Hence we have:

Adding these two yields

from which we determine

.