First, lets draw our triangle, expliciting the points coordenates:
So, A=(1,1), B=(2,4) and C=(6,3). To find the coordenates after the dilation, we just need to multiply the coordenates by the scale factor, in our case 1.5. He wants the Y coordenate of the point B, so that would be 4x1.5=6. So, our Y coordenate is 6.
