Final answer:
The question relates to solving a simple one-variable mathematical equation involving subtraction and division. The money spent on pens is $17.50, and as each pen is worth $3.50, the number of pens bought is 5.
Step-by-step explanation:
The topic of this problem involves understanding how to formulate and solve simple one-variable equations. To find out the number of pens you bought, you need to subtract your remaining money from your initial money to figure out how much you spent on pens, then divide that amount by the cost of one pen.
The initial amount of money is $26, and after buying pens, you have $8.50. The money spent on pens is therefore $26 - $8.50 = $17.50. As each pen costs $3.50, the number of pens bought, represented by 'x', can be determined by dividing $17.50 by $3.50. The equation to find 'x' is $17.50 ÷ $3.50.
The answer to the equation is 'x' = 5, so you bought 5 pens.
Learn more about One-variable Equations