What is the lmc of 3 and 7

Hello i need some with trigonometric substitutions. [tex]\int\limits^a_b {x} \, dx[/tex]

12. decide whether each statement is always true, sometimes true, or never true. a. when corresponding points of an original figure and its reflection are connected, the resulting segments are all perpendicular to the line of reflection. b. when a point is reflected over a horizontal line, the y-coordinate of the point stays the same. answer both questions and explain

Which property was used to simplify the expression? 3c+9 +4c=3c+4c+9