Question

Quantity of these two particles equals atomic weight

Answer 1

When protons and neutrons are added together it gives you the atomic #. This also serves as the number of the element

Answer 2

Protons and Neutrons.

Protons are the atomic number, subtract those from the atomic mass and you have your neutrons. That being said, add both together and you also get your atomic mass, or atomic weight.

Hope this helps!