A) 330 N
Explanation: Her weight must be evenly distributed between the chains (assuming they are at an even level), so you divide 660 by 2 and get 330
Well we can just use F=ma. The force is 10N, the mass is 50 kg, solve for a. Well since we kg and N, no conversion is necessary. So just plugging in the numbers, we get
10N = 50 kg · a

A newton is just 

The s^2 and 50 kg you multiply

The kg's cancel and 10/50 is 1/5

So the acceleration is 1/5 m/s^2