So, here you have to look at the periodic table and see what the molar mass of each molecule composing the water compound

its two hydrogen atom plus an oxygen molecule, making it about 18g per mol.
That said, looking at the mass, we have to ask ourselves, if a mol of water contains 18g of mass, how many moles do we have in 0.5g of water?
We just do a cross multiplication:
Answer:
D. The product of a constant factor 5 and a 2-term factor x+2
Step-by-step explanation:
Hope that helps
We know that
<span>Since the focus and vertex are above and below each other, rather than side by side, I know that this ellipse must be taller than it is wide.
</span>Then
a²<span> will go with the </span>y<span> part of the equation
</span>Also, since the focus is 8 <span>units below the center, then </span><span>c = 8
</span>since the vertex is 17<span> units above, then </span><span>a = 17
</span>The equation b²<span> = a</span>²<span> – c</span>²<span> gives me
</span>b²=17²-8²-----> b²=225
the equation is
y²/a²+x²/b²=1------> y²/289+x²/225=1
the answer isy²/289+x²/225=1see the attached figure