B must be 0, 1, or 2, because anything larger would cause the product 4 * (ABCDE) to be too large (it could not have 8 as the leading digit). We also know from the product that B results from 4 times something, plus a carry of 3 from the 4 * 8, so B is odd and so can only be 1. Then 4 * D plus the carry of 3 gives a number ending in 1, and by trying each single-digit number for D you see that it must be 2 or 7. It cannot be 2 because we've already used 2, so it must be 7. Now we are nearly done! We just have to solve 4 * (21C78) = 87C12 and we can finish using the same ideas. We have that 4 * 78 is 312, so 4 * C plus a carry of 3 is equal to a number ending in C. By trying all possible 1-digit values we find that C is 9. The final answer is 4 * (21978) = 87912.