So we want to know how much does the pencil costs if the ruler costs 1$ more than the pencil and together they cost 1.5$. So lets start with converting dollars into cents. Lets turn this into an equation. Ruler is x and the pencil is y. So together ruler and pencil cost 150cents or: x+y=150 cents. The ruler costs 100 cents more than the pencil, or: (x+100 cents ) + y = 150 cents. So we see that we need to put the values of x=25 cents and y=25 cents to get the ruler to cost 125 cents which is 100 cents or 1$ more than the pencil. So the pencil costs 25 cents.