Help solve math problems.

(1) The probability of encountering a red pen should be: the number of red pens/the total number of pens.

Now the probability of touching the red pen is one in four, so the number of red pens accounts for one in four.

(2) Similarly, the number of blue pens accounts for half of the total.

(3) The idea is the same as above, with red pens accounting for one twelfth, blue pens accounting for one third and yellow pens accounting for one sixth.

Pure hand tour, hope to help you!