I would say it’s better to buy the 36 box pens. 24\4.32=5.6 on the other hand the box of 36 is 36/5.76=6.25
Your proportion should look something like this

After cross multiplication, you should end up with this equation

After dividing 4 on both sides, you should get that x=9
38.2 is the quotient!!!!
Hope this helps
Answer:
x = 8
Step-by-step explanation:
Since the triangles are similar then the ratios of corresponding sides are equal, that is
= 
Note that ΔBCD is a 3- 4- 5 triangle ( Pythagorean triple), hence CD = 4
Substitute given values into the equation
=
( cross- multiply )
3x = 24 ( divide both sides by 3 )
x = 8