John is writing an article. The article is limited to 48000 words. He decides to use two types of font.Large font is 1800 words per page, small...

Let x = number of large font pages.
let y = number of
small font pages.

We'll calculate the number of pages written with
large fonts:

1 page = 1800 words

2
pages = 2*1800 = 3600 words

x pages =
x*1800

We'll calculate the number of pages written with small
fonts:

1 page = 2400 words

2 pages =
2*2400 = 4800 words

y pages =
2400y

1800x + 2400y = 48000 (1)

We also
know that John is allowed to write 21 pages:

x + y = 21
(2)

x = 21 - y (3)

We'll substitute (3)
in (1):

1800(21-y) + 2400y =
48000

We'll remove the brackets:

37800
- 1800y + 2400y = 48000

We'll combine like
terms:

600y = 48000 - 37800

600y =
10200

6y = 102

y =
17

x = 21 - y

x = 21 -
17

x = 4

The pages
written with small fonts: y = 17.