I would suggest to do future long division by learning the steps with an acronym. For me, I use DMSB, which stands for Divide, Multiply, Subtract, Bring Down. An example is attached below.
To solve this particular equation, you would get 963.33333... which would round to 963.3
The triangles are similar because of one triangle is 2x bigger than the other there seems to be a dilation. And since on triangle is 2x bigger the dilation between both triangles would be 2. I hope this helped :)
