Question 733501
to solve this problem recognize that this is a rate problem with the following equation

rate times time = distance

let t be the time it takes her to skate 4 miles and also the time it takes her to walk 2 miles, also let r+3 be her skating rate and r be her walking rate

so here we have 

(r+3)t + rt = 6 and

(r+3)t = 4   and rt = 2

expand the first equation and we get

rt + 3t + rt = 6

substitute 2 for rt and we have

2 + 3t + 2 = 6 and 3t = 2 with t = 2/3

her walking rate is r times 2/3 = 2 or r = 3 mph and her skating rate is 3 + 3 or 6 mph