Answer: 21
Step-by-step explanation: We are given that angle ABC is dilated with center P.
Scale factor=3
Angle A'B'C' is formed after dilation of angle ABC.
Dilation: when a figure is dilated by scale factor a then, the figure shape does not change.
After dilation, the size of figure changes.
The initial figure and the figure obtained after dilation are similar in shape.
When two figures are similar then , the angles of one figure are congruent to its corresponding angles in other figure and ratio of their corresponding sides are equal.
The measure of angle ABC=21'
After dilation by scale factor 3 then, the measure of angle A'B'C' remains=21'
Because the shape does not change in dilation transformation.
