Necesito que me ayuden con el tema de las rectas exteriores, interiores y fronteras. También lo de las rectas paralelas, perpendiculares u oblicuas

Find the value of x for which abcd must be a parallelogram -9-6x x-30

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”?

In trapezoid abcd, ac is a diagonal and ∠abc≅∠acd. find ac if the lengths of the bases bc and ad are 12m and 27m respectively.