Answer:
There are 75 pencils and 25 pens.
Step-by-step explanation:
If Tom has three times as many pencils than pens then,
Pencils = 3(Pens)
If there are a total of 100 writing utensils then,
Pencils + Pens = 100
Substitute the word "pencils" in this equation to 3(Pens),
3(Pens) + Pens = 100
Now remember there is almost a 'hidden' one beside the word "Pens" so,
3Pens + 1Pens = 100
Add the two together,
4Pens = 100
Divide,
Pens = 25
Substitute 25 into the first equation,
Pencils = 3(25)
Pencils = 75
Thus, there are 75 pencils and 25 pens.