Can someone help me with this math problem?

x being her average speed on the bicycle (in mph), let :
- y be her average speed in the car (in mph)
- t1 be the time spent on the bicycle (in hours)
- t2 be the time spent in the car (in hours)

The distances covered by bicycle and by car being respectively 5 miles and 40 miles we get:

x = 5 / t1
and
y = 40 / t2

plus, from the text itself (y "was 30 mph faster than" x) we have:
y = x + 30

T being the total time in hours of the trip, by neglecting any time spent during shifting vehicles we have:
T = t1 + t2

now some calculations:

x = 5 / t1
<==> t1 = 5 / x

y = x + 30
<==> 40 / t2 = x + 30
<==> t2 = 40 / (x + 30)

T = t1 + t2
<==> T = 5 / x + 40 / (x + 30)

therefore:

T = 5 / x + 40 / (x + 30)