There's two ways, you can either multiply 11 and 7 to get 77 and then divide by 2, OR, you can divide 11 by 2 and get 5.5 and multiply that by 7, hope this makes sense, if you don't understand just comment and I'll explain it more :)
When any triangle is dilated from the pre-image, its sides will never be congruent to the pre-image. However, its angles will be congruent and the triangles will be similar.
