hello I have a problem to slove

Question

At first am athlete jogs at 5 miles per hour and then jogs at 6 miles per hour, traveling 4 miles in 0.7 hour.  How long does   the athlete jog at each speed?  (hint let t represent the amount of time the athlete jogs at 5 mph.  Then 0.7 - t represents the amount of time the athlete jogs at 6 mph?)  I don't now what formula to use, I'm really lost

Answer 1

d=rt

let t=time running at 5mph

 

4= 5t+6(.7-t)

 

4=5t+4.2-6t

-t=-.2

t=.2 hours

 

he ran .2 hours at 5 mph

total time = .7 hours so he ran .7-.2 = .5 hours at 6mph

 

Check:  d = rt

          4= 5(.2) + 6(.5) = 1+3=4

answer checks