Triangle abc was dilated and translated to form similar triangle a'b'c'.

what is the scale factor of the dilation?

By the word "dilation" we mean to say that the new measurement of the sides of the triangle A'B'C' is increased by a factor from the original measurement. To determine the scale factor of the dilation, we can divide the measurement of the sides of the new triangle by the measurement of the sides of the old one. 
                           dilation factor = A'/A = B'/B = C'/C