For the first part, the results get quite crazy. I hardly believe that you're supposed to do this by hand, so I'm afraid that there's some typo in the question.
As for the second part, we have
Plug your value for x and you have
We can rewrite the quantity as
If 75% = 108 then
100% = 81
Answer: There were 741 books in the library a year later.
Step-by-step explanation:
Given: Total books in library = 570
Number of books increased by 30%.
One year later, Number of books in the library = (Total books in library) + 30% x (Total books in library)
= 570 + (0.30) x (570)
= 570 (1+0.30)
= 570 (1.30)
= 741
Hence, there were 741 books in the library a year later.
Since y=7x we can replace the y in the second equation with 7x
-5x+14x=9
x=1
Now plug in to get 7 for y, since 7x=y
Answer: x=1, y=7