The answer to the original equations is (1, -9). You can solve that by using substitution by moving the 4y over and substituting that equation for x on the second part of the top equation. Using elimination, the second set of answers will give you the same, (1, -9)!
It would be 7 hours because 35 x 3 is 105, if she is already 105 miles from home then 35 x 7 is 245. 245 + 105 = 350. Candice would be at 350 and Liz would be at 350, so in conclusion the answer is 7 hours. :)