No 6 is common for N and H. 3 is only for H(Hydrogen).
For finding the number of hydrogen atoms we should multiply 6 with 3
So, 6*3 = 18. So there will be 18 hydrogen atoms in 6NH₃
The answer is A
he is known as the father of natural selection :D
The efficiency indicates the manner in which the inputs are used by the system. Being efficient means the system uses inputs in a `right' way. If the input-output ratio is adverse, we say that the system is inefficient though it produces the desired output.
I'm pretty sure they are called autosomes