An atom with 7 protons, 6 neutrons, and 7 electrons has an atomic mass of amu

The atomic mass of this element would be 13 amu.

Explanation:
The subatomic particles provide several bits of information about a given element.
The number of protons is equal to the atomic number of the element. For this element having 7 protons makes the atomic number 7 and makes the element Nitrogen.
The number of protons plus the number of neutrons equals the atomic mass of the element based upon atomic mass units (amus).
For this element 7 protons and 6 neutrons combine to make an atomic mass of 13 amus.

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Yes you are correct use the scientific method