When the jumper jumps off , there is always a force of gravity acting on her which is 55*9.8 =539N downwards. (Considering the acceleration due to gravity to be 9.8)
Since the question says that the force exerted by cord is 825N upwards , it is obvious that the pseudo force of acceleration must act downwards and the jumper must be moving upwards.
Assume the acceleration at that instant be 'a' .
Pseudo force = mass * acceleration = 55*a
Since the body is in dynamic equilibrium , all forces must cancel out.
Hence ,
539 +55*a = 825
=> 55*a = 825-539 = 286
=> a = 286/55 = 5.2
So , acceleration at that instant was 5.2 m/s²
