How to calculate f?

[still olive]

hi

[viral wren]

i ain't trying to read that

the black grid lines makes it very hard to read

can you just post the question

a lot of the times, the best way to help is for me to do it myself first, then compare what we did

[chilly cave]

Provide the original Question, preferably English.

[velvet saffron]

you don't need that alpha between 7 and 8. Find the other two angles instead, say, between l and 5 and between l and 7. Then use the law of cosines to find f.