Question

.

Answer 1

the answer must be 12/5

Answer 2

\[\frac{4\times 6}{4+6}\]

Answer 3

rate times time = work
so you have 1 work with two rates and unknown time

Answer 4

\[(\frac{ 1 }{ 4 }+\frac{ 1 }{ 6 }) t = 1\]

Answer 5

find t, be 2.4 hrs

Answer 6

as @Jeffrey_Calderon said find \(t\) via
\[(\frac{1}{4}+\frac{1}{6})t=1\]
\[\frac{6+4}{6\times 4}t=1\]
\[t=\frac{6\times 4}{6+4}\]
if you do more than two of these the pattern should be clear and you can skip all the middle stuff
adam take \(x\) hours to complete the job, eve takes \(y\)
working together it takes them \(\frac{x\times y}{x+y}\) hours