**Solution :-** Let present age of one friend be x and that of the other 20 – x.

4 years ago age of first friend = x – 4, and that of the other = 20 – x – 4 = 16 – x.

According to question, (x – 4 )(16 – x ) = 48

Or, 16x – x^{2} – 64 + 4x =48

Or, x^{2} + 20x – 112 = 0

Or, x^{2} – 20x + 112 = 0

Here, a = 1, b = – 20, c = 112

D = b^{2} – 4ac = (– 20 )^{2} – 4 ×1 × 112 = – 48 < 0.

Hence, the given situation is not possible.