Combine 3 measures into one DAX expression?

Hi there!

I currently make a new measure every time I need to alter or calculate a result to display in my tracking dashboard.  Can you help me combine all of these to get the intended result?

First, I calculate the date to get the date that the last MX was completed:

Last 200hr MX Date = CALCULATE(MAX(xxData[Date]),CONTAINSSTRING(xxData[Comments], "MX"))

Calculate the number of hours since that date:

Hours since 200hr MX = 
VAR LastMX = [Last 200hr MX Date]
RETURN
    CALCULATE(SUM(xxData[Flight Hours]),dimDate[Date]> LastMX)

Divide the number of hours by 18, remove any decimals, and add " flights" to the end:

final200 = 

VAR c200 = (200-[Hours since 200hr MX])/18
        RETURN
        TRUNC(c200) & " flights"

I lack the coding experience to string these all together in one function.  Can anyone help?  Also need to make it so it does not return a negative number, only 0 as the lowest possible result.

Thank you!