Answer:
<h2>x = 12</h2>
Step-by-step explanation:
ΔADC and ΔCDB are similar (AA). Therefore the sides are in proportion:

We have AD = 16, DC = x, DB = 9. Substitute:
<em>cross multiply</em>

So chance to get a black pen: 4/10=2/5
Chance to get a red pen: 1/10
Chance for the two happened at the same time
2/5 * 1/10 = 2/50=1/25
I think... I’m not very sure though
X^2+2x^2-5x
((x^2)+2x^2)-5x
Pull the factors out
3x^2-5x=x(3x-5)
x(3x-5)
x(3x-5)*5x^2
5x(3x-5)*x^2
Final
5x^3*(3x-5)
So 2% is 2/100. That would be 0.02.