Keep note of these things before we start:
-Of is a keyword that tells us multiplication is being done
-x = total number of pages
-32% = 32/100 = .32
Okay, here we go:
32% of total number of pages = 80
.32 of x = 80
.32*x = 80
.32x = 80
.32x/.32 = 80/.32
x = 250
There are 250 pages in total in Katie's book.
To find out how many pages she has to read (y), subtract the pages read from the total:
TOTAL - PAGES READ = PAGES LEFT TO READ
250 - 80 = y
170 = y
Katie has 170 pages left to read
Hope this helps!