What is amu of 99 % H-1,.2% H-1 and. 8% H-3

The average atomic mass of your mixture is 1.03 u.

The average atomic mass of H is the weighted average of the atomic masses of its isotopes.

We multiply the atomic mass of each isotope by a number representing its relative importance (i. e., its % abundance).

Thus,

0.99 * 1.01 u = 0.998 u

0.002 * 2.01 u = 0.004 u

0.008 * 3.02 u = 0.024 u

TOTAL = 1.03 u