I don't know for sure, but I think there might be an error in the way you copied your function. In all of my dealings with these types of problems, I have learned the formula to be h(t) = 15 + 10t - 16t^2. Notice the plus in front of the "10t". This is due to the fact that if he pushes off of the overhang he would have an upward force of 10 feet per second as soon as his feet left the ground. The only thing pulling him back to Earth is gravity, modeled by the "-16t^2". This is derived from a bit of slightly advanced physics involving the gravitational constant, but let's work under my formula for a second...
Either way, we will wind up using the Quadratic Formula (or possibly factoring if the numbers are easy enough to work with). So let's start.
h(t)= 15 +10t - 16t^2
In order to use the QF or factoring I will need to make h(t)=0. Simply done by:
0= 15 +10t -16t^2
Looking at the numbers, I'd prefer to use the QF so here it is:

I know that my answer will need to be positive since you can't have a negative value when dealing with time, so I will eliminate the positive sign from the "+or-" part leaving me with:

And I know that a= -16, b= 10, and c=15. So all that's left to do is substitute and solve.
There's a decent amount of math that would be difficult and sloppy for me to do over the computer, but all you need to do is solve the rest of the equation and you would get your answer.
Exact answer:

or rounded answer: ≈1.31 seconds.
Hope this helps!
NoThisIsPatrick
Each foot of the real desk will be 0.5 on the dolls desk.
3ft x 0.5 in per ft = 1.5 inches
Answer: ABCD is a parallelogram.
Step-by-step explanation:
First we plot these point on a graph as given in attachment.
From the attachment we can observe that AD || BC || x-axis .
also, AB ||CD, that will make ABCD a parallelogram , but to confirm we check the property of parallelogram "diagonals bisect each other" , i.e . "Mid point of both diagonals are equal".
Mid point of AC= 
Mid point of BD= 
Thus, Mid point of AC=Mid point of BD
i.e. diagonals bisect each other.
That means ABCD is a parallelogram.
Answer:
1. <2, <7
2. 58
3. 78
4. a and b
h5. <2 and <7 ( i think this is the same question as the first one)
Step-by-step explanation:
2. 2x + 7 = 123 (you have to make them equal to each other because they are consecutive interior angles)
2x + 7 = 123, subtract 7
2x = 116, divide 2 for both sides to make x by itself
x = 58
3. 78 because of consecutive interior angles