"Mya bought several packs of pens for her office. Each pack contains the same number of pens. If she has a total of 21 pens, how many packs of pens did Mya buy?"
To solve this problem, we can use the equation 3x = 21, where x represents the number of packs Mya bought. By dividing both sides of the equation by 3, we find that x = 7. Therefore, Mya bought 7 packs of pens.