Answer:
as triangle is a right angle triangle .
you can apply trigonometric ratios .
by tan theta = perpendicular / base
tan 55° = 12/x
x = 12/ tan 55°
put the value of tan 55 ° here .
as I don't know the value of tan 55° as it was not present in my syallabus still now .
hope you will get the idea .
hope this will be helpful to you.