Respuesta :
Answer:
Lucy had 40 books last year.
Step-by-step explanation:
assuming 100% is the percent;
100% + 70%
100 : x
170 : 68
cross multiply = 170x = 100 x 68
-------- ————-
170 170
cancel 170/170
therefore x = 100 x 68 divided by 170
result is 40