What was the initial distance from the shuttle to the astronaut?

Edit: In application of momentum, the most important law to know is the Conservation of Momentum. Momentum is said to be conserved when there is zero net external force acting on the object. So mathematically:
Definition of momentum: p = mv
Newton's 1st law: F = ma => m dv/dt = dp/dt
Net external force is zero: F = 0 => dv/dt = 0
dv/dt = 0 => Dp = 0
Conservation of Momentum is mathematically expressed as:
mv(initial)  = mv(final)
Hence in this case:
v = d /t = d/7.5
by conservation of energy:
1200 * 0.15  = 90 * d /(7.5)
d = 15 m