What is the molarity of a solution prepared by diluting 150. ML of 0.484 M HNO3 to 450. ML

Concentration1 x Volume1 = Concentration2 x Volume2

0.484M x 150mL = your answer x 450mL

just rearrange

I used to really stuggle with these kind of questions (still have my moments!)
This book was really helpful

Calculations for A level Chemistry