New to chemistry, please teach me the calculation!!

i've 2 questions that i don't know how to do, looking through my
textbook for hours still i couldn't get the answers they provided.
Can anyone please show me how to do them with the work shown?

Here are the questions.

1)The important metal titanium has five naturally occuring isotopes on
Earth. However, the percentages and isotope distribution could vary
if titanium were found elsewhere. For example, hypothetically we
could analyze a sample from the moon and find the following: Two
titanium isotopes were found; one with a mass of 47.9479 amu and a
percent abundance of 81.533. If the weighted atomic mass of the
titanium in this sample was 47.5268 what would be the mass (in amu)
of the second isotope? How many significant figures should the answer
have? Enter your answer as an integer.

correct answer: 45.668 amu ± 2.0%
5 significant figures

2)The anti-tumor agent cisplatin is 65.0% platinum. How many grams
(use g for the unit) of cisplatin could be synthesized with 1.22 mg
of platinum? How many significant figures should the answer have?
Enter your answer as an integer.

correct answer: 0.00187 g ± 2.0%
3 significant figures.

please teach me, I know they are easy for you guys, but i'm totally
new to chemistry and need to know the way to do them. I need to
practise more for my coming up exam, so please show me the
calculation of solving the problems, I really appreciate you.
Thanks!!!



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