Find the amount Atoms and the total amount of elements for each formula

Question

C4H10 2 elements 14 atoms

H4Mg3Si2O9 4 elements 18 atoms

C6H7O2(OH)3 3 elements 18 atoms

Pb(NO3)2 3 elements 9 atoms

Answer 1

Yes

Answer 2

Thank you

Answer 3

You are welcome

Answer 4

I disagree with C6H7O2(OH)3. There are 21 atoms.
C = 6
H = 7
O = 2
(OH)3 = O = 3 and H = 3
Total 21