Help me with gas laws in chemistry with math

Question

A 75 L sample of dry air cools from 147°C to -37°C while the pressure is maintained at 2.85 atm. What is the final volume?

Answer in units of  L

Answer 1

Part 1: solve for n (number of moles)

PV = nRT

(2.85) (75) = (n) (0.08206) (420.15)

213.75 = 34.478 (n)

213.75 / 34.478 = n

6.1996 = n

Part 2: use n to solve for final volume

PV = nRT

(2.85) (V) = (6.1996) (0.08206) (236.15)

(2.85) (V) = 120.139

V = 120.139 / 2.85

V = 42.154

Answer:

42L