Form 4 physicis

u = 6
v = 12
t = 3
by a = (v-u) / t
a = (12 - 6) / 3
a = 2ms^-2
by s = ut+1/2at^2
s = (6)(3) + 1/2(2)(3)^2
total distance = 27m

Since accelerates uniformly,

s = (u + v) x t / 2

s = (6 + 12) x 3 / 2

s = 27 m