Element W has two natural isotopes: W-10 (10.013amu) and W-11 (11.009 amu)

Calculate the atomic mass of element W given the abundance of W-10 is 19.66%

I thought that I needed abundance for both isotopes to solve the atomic mass? I’m really bad at Math and Chemistry... I thought I was understanding how to solve atomic mass and now I can’t figure out this question. I asked my prof for help but he used an example where we were given abundance and amu for all the isotopes and just had to use the average atomic mass formula.

I don’t know how to go about this question, could someone please show/explain to me how to do it?

TIA

-badatmath