I can't see the options, but you would need to multiply (4x - 2y = 7) by 3, and (3x - 3y = 15) by 4 so that you get 12x in both equations. Then when you subtract, you eliminate 12x. I hope this helps!
Your answer here would be A. because every hour she travels 3 miles so 3h. (3 × h). Then you add the 5 miles you know she at least walked. Put it together and you get 3h + 5. Hope this helped :)