Which equation will determine how long it would take them to work together

Answer:
Tyrell can do 1/4 of the work in 1 hour
And Hunter can do 1/6 of the work in 1 hour
So if they work together
they will do (1/6 + 1/4 = 5/12 ) of the work in 1 hour
So if 5/12 is done in 1 hour the whole work is done at 12/5 hour which is equal to
2 hours and 24 minutes