Math Help

Sorry to be a bother guys, i'm about halfway through my sheet...and I wasn't doing too bad up until this...

So basically its a word problem.

A movie stuntman jumped from a tower and fell for several seconds before relasing a parachute. His height, h (in metres) and t (time) after jumping is modelled by...

$ h=-4.9t^2+t+350 h= -4t + 141 $ errr.. there is a space between the 350 and h

How long after jumping did the stuntman release his parachute?
How high was he when he relased it?

I can tell you now that you would probably have to complete the square using both equations somehow....except i'm not quite sure, or if I have to do some substitution. Any help would be great....

And if you have time....

$ X^2 + y^2 = 13 2x + 3y = 12 $

its not 132 x its 13 then a seperate eqaution 2x.

I can't seem to solve that for some reason, its probably just me making a stupid mistake... (Wondering)

and i'm gonna try to give help around here if I can... haha.