nomer 2 tolong ya, thanks

Misal laju v dan jarak s : v = s/t => s = v.t
1) jika lajunya bertambah 3 km/jam, sampai 40 menit lebih cepat = 2/3 jam
s = (v + 3).(t - 2/3)
s = vt - 2/3 v + 3t - 2
s = s - 2/3 v + 3t - 2
2/3 v - 3t = -2

2) jika laju berkurang 2 km/jam, sampai 40 menit lebih lambat = 2/3 jam
s = (v - 2)(t + 2/3)
s = vt + 2/3 v - 2t - 4/3
s = s + 2/3 v - 2t - 4/3
-2/3 v + 2t = -4/3

Eliminasi
2/3 v - 3t = -2
-2/3 v + 2t = -4/3
--------------------- +
-t = -10/3
t = 10/3 jam

2/3 v - 3t = -2
2/3 v - 3(10/3) = -2
2/3 v - 10 = -2
2/3 v = 8
v = 8 . 3/2 = 12 km/jam

Jarak = s = vt = 12 km/jam . 10/3 jam = 40 km