The GCF of the first two is 4p³q².The GCF of the second two is 8pq⁵.The GCF of the third two is 4p²q⁵.The GCF of the fourth two is 8p²q.The GCF of the fifth two is 4p²q. To find the GCF of each pair, find the greatest number that will divide into each coefficient. As for the variable portions, choose the variable that has the smallest exponent from each pair.
Your distance is 1424 and your rate is 356. As you said, d = r*t. Since you don't have the time you would do 1424 divided by 356. This leaves you with a time of 4 hours. (Don't forget units!)
