Vertex at the origin and opening down → y=ax^2
Width: w=16
x=w/2→x=16/2→x=8
x=8, y=-16→y=ax^2→-16=a(8)^2→-16=a(64)→-16/64=a(64)/64→-1/4=a→a=-1/4
y=ax^2→y=-(1/4)x^2
7 m from the edge of the tunnel → x=w/2-7=8 m-7 m→x=1 m
x=1→y=-(1/4)x^2=-(1/4)(1)^2=-(1/4)(1)→y=-1/4
Vertical clearance: 16-1/4=16-0.25→Vertical clearance=15.75 m
Please, see the attached file.
Answer: Third option 15.75 m
Answer:
B) -3
Step-by-step explanation:
1. First you have to write the equation in slope intercept form. To do that, you must have y be alone on one side.
2. move the 3x to the right side with the 5 by subtracting 3x from both sides. Since 3x will cancel on the left, y will be left alone. 
3. Now that you're in slope intercept form, you can find the slope easily. The slope will always be the number in front of x. In this case, the number in front of x is -3. Therefore, -3 is your slope!
Height would be 21 inches, depth would be 5.