The ratio of the number of pencils to the number of pens John bought was 3:2. Each pen cost $9 while each pencil cost 1/3 as much as a pen. He paid a total of $108 for all of them. How much more did John spend on the pens than on the pencils?
Each pencil must have cost $3
So...... using a bit of logic
3 pencils cost $9 and 2 pens cost $18 = $27 total
So multiplying each quantity by 4 we have that
12 pencils cost $36 and 8 pens cost $72
So $36 + $72 = $108
And he spent $36 more on pens than pencils