Finding mass based on amu and % abundance

[chemstudent]

Homework Statement

Oxygen has 3 isotopes. Oxygen-16 has the amu of 15.995 and its natural percent abundance is 99.759. Oxygen-17 has a mass of 16.995 amu and its natural percent abundance is 0.037. Oxygen-18 has a mass of 17.999 amu and its natural percent abundance is 0.204. What is the average atomic mass of oxygen?

Homework Equations

I think I forgot these...

The Attempt at a Solution

I couldn't remember what the process is supposed to look like to figure this sort of problem out, so I tried to multiply the mass by the percent abundance, but the answers made very little sense. If somebody could help me figure out where I messed up, PLEASE RESPOND!

 

[symbolipoint]

The average atomic mass of an element is much like a simple mixture problem that you learn in first year Algebra such that you can resort directly to percentage contributions formula.

AverageAMU = 0.99759*16 + 0.00037*17 + 0.00204*18

 

[chemstudent]

Thank you so much!