Answer
$weight = 780~N$
Work Step by Step
We can convert 175 lb. to units of kg.
$(175~lb.)\times \frac{1~kg}{2.2~pounds} = 79.55~kg$
We can find the weight of the astronaut in newtons:
$weight = mg$
$weight = (79.55~kg)(9.80~m/s^2)$
$weight = 780~N$