Recall that the interior angles of a triangle add up to 180 degrees, therefore we can set the following equation:
[tex]6x-16+6x+19+57=180.[/tex]
Adding like terms we get:
[tex]12x+60=180.[/tex]
Subtracting 60 from the above equation we get:
[tex]12x=120.[/tex]
Finally, dividing by 12 we get:
[tex]x=10.[/tex]
Answer: x=10.
