Shawn's answer to SHREYA's Primary 6 Maths Algebra Singapore question.

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Shawn
Shawn's answer
110 answers (A Helpful Person)
1st
If n = 5, the number of files she bought will be 15.

If 1 notebook cost $25 more than a file, there are a total of 5 notebooks’ difference to minus off from the total.

$25 x 5 = $125
$160 - $125 = $35
“20 files” = $35
1 file = $35 / 20
= $1.75

If you remove the difference between a notebook and a file, you will get the price of a file. For example, let the price of a file be x.
1 notebook is $25 more than a file,
Notebook = x + $25
5 notebooks = 5(x + $25)
= 5x + $125 [5x is the same as 5 files]
15 files = 15x
Total $160 = 15x + 5x + $125