Step-by-step explanation:
if you're looking for x
x=180-42-51= 87°
and if you're looking for D
D= 180-42= 138°
Let's call the number you thought of n. Then what the two steps you took can be written as an equation:

Subtract n to get all of your variables to one side:

At this point, I recommend turning your mixed number into an improper fraction. It will make things easier later on:

Now divide both sides by 11 to get the value of n:
Answer: 384
There are 384 smoke free rooms.
So the first two questions are asking for points of intercept. a is asking where the function crosses the x, in this case it is where y=0. So your x intercept is at x= 1,5. Then to find the y intercept it is where x=0, so just substitute 0 for x. Then you get your y intercept as y=5. Because your coefficient for the quadratic function is positive your function has a minimum since it opens upward. I’m not sure what is means by C coordinate, but your vertex is at (3,-4) and lime of symmetry is at x=3.
X intercepts: (1,0) and (5,0)
Y intercept: (0,5)