Lets say she buys 8 more pencils to make it the same number as erasers bought.

8 x $1 = $8

she will spend $8 more. And since she previously spent $4 more pencils,

$4 + $8 = $12

Now she would have spent $12 more on pencils than erasers.

Difference in pencil and eraser cost
= $1 - $0.60 = $0.40

Since she has same number of pencils and erasers now,

$12 ÷ $0.40 = 30

30 pencils cost $12 more than 30 erasers.

So number of erasers bought = 30

But remember she didn't actually buy that 8 pencils, we just pretended she did.


So actually number of pencils bought
= 30 - 8 = 22

Thanks