Well knowing these are both obtuse angles of the same shape and size we can begin. were looking to show AC is equal to DF we start by connecting A to C. A goes to C and makes this half an Oval shape along the bottom line now try connecting A to B and C to B AB and CB are not the same as AC and since these angles are the same shape and size we know DF should do the same so now we connect D to E and F to E similar to AC they do not match nor do they match AC itself leaving us to compare D to F after we do this we see that it creates the same sized half an oval as AC showing us that they are equal. :)
Well since you're using 3/8 and you need to make 4 batches, you need to multiply 3/8 with 4 it would equal 12/8 or 1 4/8 (I could be wrong but this is my answer hopefully this helps) :) <span />