To solve this problem, we can use the fact that the exterior angle of a triangle is equal to the sum of the two opposite interior angles. Let's call the unknown interior angle opposite to the given exterior angle "a". Then, we have:
a + 76° + 90° = 180°
Simplifying and solving for "a", we get:
a = 14°
Now, we can use the fact that the angles in a triangle add up to 180° to find the value of "x". We have:
x + 90° + a = 180°
Substituting the value of "a" that we found earlier, we get:
x + 90° + 14° = 180°
Simplifying and solving for "x", we get:
x = 76°
Therefore, the value of x is 76°.