How many atomic mass units are equal to 1.672×10−24 g of protons?

1.0 amu.

Explanation:

Using cross multiplication:

1.0 g → 6.022 × 10²³ amu.

1.672 x 10⁻²⁴ g → ??? amu.

∴ the number of atomic mass units in 1.672 x 10⁻²⁴ g of protons = (1.672 x 10⁻²⁴ g) (6.022 × 10²³ amu) / (1.0 g) = 1.00687 amu ≅ 1.0 amu.