Does a=2.1 b=7.2 c= 7.5 make a right triangle

One month, a music site observed that 60% of the people who downloaded songs from its site downloaded q sam's latest single. the equation below represents this information, where x represents the total number of people who ddownloaded songs from the site that month: x = 0.6x + 384 how many people who downloaded songs from the site that month downloaded q sam's latest single?

What is the missing reason in the proof? segment addition congruent segments theorem transitive property of equality subtraction property of equality?

Which two undefined geometric terms always describe figures with no beginning or end?