The "time" equation is= , where x is the unknown rate of the current; d is the on way distance. We can cancel the factor d in both sides. Then we have = . To solve this equation, first cross-multiply; then simplify 8 + x = 3*(8-x) 8 + x = 24 - 3x x + 3x = 24 - 8 4x = 16 x = 16/4 = 4. ANSWER. The rate of the current is 4 km/h.