Question

to prepare 50.0 g of 10% NaNo3 solution you will need how many grams of solute

Answer 1

0.1 x 50 = ?

Answer 2

I'm writing this after reading your first post.
10% w/w means you want 10g solute/100 g solution; therefore, to make only 50 g total you will need just half that or 5 g.