If she runs four days a week at x miles a day then the number of miles in that week is 4*x miles. x increases 0.5km per week. The second week will give x = 1.5 + 0.5 = 2.0km. Try using that pattern to get the other weeks.
I have no idea because of the ambiguous nature of the question whether or not the next week includes 7 days or just 3 ''In preparation for the 10km mini marathon , maray starts training. she plans to run 1.5km four days this week. Each week she plans to increase the distance she runs each day by 0.5km(i) write down the distance she plans to run in the second , 3rd and 4th week of her training programme
Maray runs four days a week and 1.5 km each day. So distance covered each week is 1.5 * 4 = 6 km
Increases 0.5 km per day so in a week she increases 2 km
Thus second week she would cover 6 + 2 = 8 km and third week 8 + 2 = 10 km and so on.