The gene for hair type is represented by the letter H. Curly hair is dominant to straight hair. What letter would best represented the allele for straight hair?

S , h it’s a type of curl

To determine the average atomic weight of the hypothetical element X, you essentially take the average of the isotopes based on the percent abundance of each isotope present.

However, to do this "without doing an actual calculation" is not possible. But we can do it with very simplified calculations. We have one isoptope of X that is 42 amu that is 1/3 of the element, and the other isotope which is 45 amu that is 2/3 of the element.

A simple calculation to find the mass of X is as follows:

(1/3)(42 amu) + (2/3)(45 amu) = atomic weight of X.
14 + 30 = atomic weight of X
Atomic weight of X = 44 amu.

The mass closest to the atomic mass of X is 44 amu.