Can you explain how my practice book achieved this answer,

53') Find the new vertices of a triangle with vertices (2, 3), (2,7), (6, 3) after it ' has bEen rotated clockwise by 90 and then compressed vertically by a factor-of; Then nd the area of the resultant triangle. Answer: Set up a matrix using the vertices of the triangle. O 'l 2 2 6 {1 '0] [3 7 3] Multiple by the appropriate matrix _ 3 7 3 to rotate the triangle clockwise 90. ' {2 _2 6] Multiple by the appropriate matrix to compress the rotated triangle. Use the formula to nd the area of the new triangle using the determi nant. The area of the triangle is 4 units