Answer:
There is no problem. If you put the problem then i'll help
Step-by-step explanation:
For problems like this you can move the y's on the bottem up top by fliping the sign of the exponent (in this case 7 to -7) and MULTIPLYING it with EVERYTHING on top, then because of properties of multplication you can add the exponents to combine them into one term (in this case add 3 and -7 to get -4)

If any of this does not make sense let me know and ill try to clarify better
Answer:
V = D/t = 10 / 20 = 0.5 mile per min
V = D/t = 20/30 = (2/3) mile per min
V = D/t = (10+20)/ 50 = (3/5) mile per min