Hard - form simutaneous equation

May 2010
This one has had me stumped for a few days now. Hope someone can help shed some light on this question.

1) For a body travelling with constant acceleration of a meters/second^2 its velocity Vm/sec after t seconds is given by V=u+at where u is its initial velocity.

After six seconds the body had a velocity of 30 metres per second. 10 seconds later its velocity V was 70m/sec.

Form a pair of simultaneous equations and solve them to find:
a) the acceleration
b) the intial velocity
c) the velocity after 20 seconds