which statement is sometimes, but not always, true?

a.
a trapezoid is a quadrilateral.

b.
a parallelogram is a rectangle.

c.
a rhombus is a parallelogram.

d.
a rectangle is a polygon.

Write an explicit formula that represents the sequence defined by the following recursive formula:

Scores on a university exam are normally distributed with a mean of 78 and a standard deviation of 8. the professor teaching the class declares that a score of 70 or higher is required for a grade of at least “c.” using the 68-95-99.7 rule, what percentage of students failed to earn a grade of at least “c”?

Gabrielle's age is two times mikhail's age. the sum of their ages is 84. what is mikhail's age?