Susan enlarged a rectangle with a height of 6 cm and length of 13 cm on her computer. the length of the new rectangle is 19.5 cm. find the height of the new rectangle.

We have that enlarging the rectangle in a computer setting keeps the ratio of the lines constant. Hence, height over length is the same. For the first rectangle this is 6/13. For the second one, if x is the new height, this is x/19.5.
Hence x/19.5=6/13. Multiplying both parts by 19.5 we have that x=19.5*6/13=9. Thus, the new height is 6 cm.