All we need to do is to find out how many 0.8-foot elements can fit in 6.7-feet plank. To do that we may just do the division:
6.7 ÷ 0.8 =
= 67 ÷ 8 =
= 8,375
As we can see, Arancha can make 8 elements and a little bit of 9th element, but as long as she may not want any smaller element, we can say that she'll have 8 0.8-foot elements from 6.7-feet plank.