Question

kevin goes at a speed of 21kmph instead of 15kmph then he would have crossed 40 km more what is the actual distance travelled by him

Answer 1

( I don't know exact answer. Just bny guessing )
we can use inverse variation method
  speed (kmph)       distance (km)
        21                         40 + x
       15                               x

21 * (40 + x)   =  15 x
840 + 21x       = 15 x
 840                = -6x
    x      = 140 km