Nice work on getting part (a) correct.
The 261% falls in the "250-300%" range, so they pay 8.5% of their yearly income toward health insurance.
8.5% of $65,500 = 0.085*65500 = 5567.50
That represents the yearly contribution. Divide that by 12 to find the monthly contribution.
5567.50/12 = 463.95833 = 463.96 approximately
Then round to the nearest dollar to get 464
Answer to part (b) is 464