The product of 9 and a number is 12 less than three times that number.
what is the number?

Product means multiplication
is means equal
less than means subtraction
times means multiplication

The product of 9 and a number is 12 less than three times that number.

Lets say this number is 'n'

then:

9n = 3n-12

Add 12 on both sides

9n + 12 = 3n

Subtract 9n on both sides

12 = -6n

Divide by -6 on both sides to isolate n

n= -2

Your final answer is 

1. statement- ca is parallel to db and e is the midpoint of ad reason- given2. statement- reason- alternate interior angles3. statement- de is congruent to ae reason- definition of midpoint4. statement- triangle aec is congruent to triangle deb reason- asa (angle side angle)