Element X has two isotopes in nature.One isotope has an atomic mass of 1069 amu with 50 percent. The atomic mass of the other isotope is 109,91 amu?

To find the atomic mass of Element X, we can use the weighted average formula:

Atomic mass = (% abundance of isotope 1 * atomic mass of isotope 1) + (% abundance of isotope 2 * atomic mass of isotope 2)

Plugging in the values given:

Atomic mass = (0.50 * 106.9 amu) + (0.50 * 109.91 amu)
Atomic mass = 53.45 amu + 54.96 amu
Atomic mass = 108.41 amu

Therefore, the atomic mass of Element X is 108.41 amu.

Let the abundance of the isotope with an atomic mass of 106.9 amu be x%. Then, the abundance of the isotope with an atomic mass of 109.91 amu is (100 - x)%.

According to the given information, we have:

```
(106.9 - x/100) + (109.91 - (100 - x)/100) = average atomic mass
```

Substituting the given values:

```
(106.9 - 50/100) + (109.91 - (100 - 50)/100) = average atomic mass
```

Solving for the average atomic mass:

```
(106.9 - 0.5) + (109.91 - 0.5) = average atomic mass
```

```
53.45 + 54.955 = average atomic mass
```

```
average atomic mass = 108.405 amu
```

Therefore, the average atomic mass of element X is 108.405 amu.