The equation is a scientific law, Newton's Law of Gravity,

This is a pretty bad question. Newton's Law of Gravity is a mathematical model of gravitation, originally a theory, verified by observation, and now superseded by the General Theory of Relativity.
C is probably the best answer to this poor question.
the assumption being that the first machine is the one on the left-hand-side and the second is the one on the right-hand-side.
the input goes to the 1st machine and the output of that goes to the 2nd machine.
a)
if she uses and input of 6 on the 2nd one, the result will be 6² - 6 = 30, if we feed that to the 1st one the result will be √( 30 - 5) = √25 = 5, so, simply having the machines swap places will work to get a final output of 5.
b)
clearly we can never get an output of -5 from a square root, however we can from the quadratic one, the 2nd machine/equation.
let's check something, we need a -5 on the 2nd, so

so if we use a "1" as the output on the first machine, we should be able to find out what input we need, let's do that.

so if we use an input of 6 on the first machine, we should be able to get a -5 as final output from the 2nd machine.

Answer:
All real numbers
Step-by-step explanation:
Let's solve your inequality step-by-step.
−x2−6<0
Let's find the critical points of the inequality.
−x2−6=0
−x2−6+6=0+6(Add 6 to both sides)
−x2=6
−x2
−1
=
6
−1
(Divide both sides by -1)
x2=−6
x=±√−6(Take square root)
Answer:
yea
Step-by-step explanation:
Y=4.1 because it if take ten. And multiply it by three then take negative 9Y equals seven and divided by nine gives you 4.1