Step-by-step explanation: the way you know is because the angles on each shape are the same and the lines on the shapes are the same length. If one shape is bigger than another or if one has a different shape than the other, they are <u>not</u> congruent. I hope that helped you!
$2.50+3x=$9.25, if you need to work it out, then you do $9.25-$2.50. You take your answer and divide by three... whatever your solution is, equals X. There you go!