Because we times hight by width when it comes to triangles we times these two together to make 4, but because it is a triangle we simply just half the product. Thus your answer 2 units^2
$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!