Al fotocopiar una credencial, primero se amplia al triple y posteriormente la copia resultante se reduce a la mitad. ¿cual es el efecto final respecto a la credencial original? si al credencias es un rectángulo de 10 por 6 cm. ¿que área tendrá en la primera fotocopia? ¿y en la segunda?

Using google translate: 
When photocopying a credential, it is first enlarged to triple and subsequently the resulting copy is halved. What is the final effect on the original credential? If the credentials is a rectangle of 10 by 6 cm. What area will you have in the first photocopy? And in the second?

Original: 10 by 6 cm  ;  Area = length * width = 10 x 6 = 60 cm²

first copy: enlarged to triple
10 x 3 = 30 
6 x 3 = 18
30 x 18 = 540 cm²

second copy: halved
30 x 1/2 = 15
18 x 1/2 = 9
15 x 9 = 135 cm²

Are you asking for 6 or 15?

so the perpendicular line goes through the given pointyou would get a perpendicular line at some random location

step-by-step explanation:

points a and b are equidistant from the desired line, so the line you find by using them will go through point r.

using points other than a and b will give the desired line only if they are equidistant from r. if they are randomly located, the perpendicular line you create will not necessarily go through point r, hence will not be a solution to the problem.