Help with general trig equation

I don't know what this problem would be classified as, but i need help with it!

The formula **F(x)=75+15sin[2π/365(x-101)]** represents the fahrenheit temperature in Gainesville as a function of the day of the year. Let x represent the day of the year (in a non leap year), so **x=1** represents Jan. 1 (etc.) Use this formula to determine the day(s) of the year (give the dates) when the average daily temperature will be closest to **85ºF**

I graphed it in a graphing calculator and determined that the days were day 143 and day 240 (April 23rd and July 28) and plugged them into the equation and they equaled about 85, but i do not know how to work the problem out using trig functions.

Any help would be appreciated. Thank you!