How do I do this?

Let the distance of the train=D, then

Let the time taken to travel to her grandparents=T

T=D/82

t=D/41

D/82 + D/41=6

3D/82=6

3D=492

D=164 miles

164/82=2 hours to travel to her grandparents

164/41=4 hours to travel back home.

The answer is: C.

82*1=82                                  The second numbers must add up to be 6. The solutions must be the same, as                                                              she is travelling the same distance both ways. There are multiple wasy to solve btw.

82*2=164

82*3=246

82*4=328

82*5=410

82*6=492

41*1=41

41*2=82

41*3=123

41*4=164

41*5=205

41*5=205

Distance/Rate  = Time   .......so.....

Time traveled on Friday + Time  traveled on Sunday  = Total Time

D/82 + D/41   =  6   where D is the one-way distance.....    get a common denominator

[D + 2D] / 82  = 6     simplify and cross-multiply

3D  = 492

D = 164

So....the time on the train on Friday  =

164 / 82   = 2 hours

Her combined average speed=41 + 82=123 mph, therefore,

(41/123) X 6=2 hours to travel to her grandparents.

(82/123) X 6=4 hours to return home.