Question 41238
5a - 12/a^2 - 8a + 15 minus 3a -2/a^2 - 8a + 15

I understand the question like this; 
(5a - 12)/(a^2 - 8a + 15) minus (3a -2)/(a^2 - 8a + 15)

Since the denominators are the same we can subtract the numerators from each other;

((5a - 12)-(3a -2))/(a^2 - 8a + 15)= (5a-12-3a+2)/(a^2 - 8a + 15)=
(2a-10)/(a^2 - 8a + 15)

Now let's factor the numerator;

2a-10 = 2(a-5)

And if we factor the denominator;

a^2 - 8a + 15=(a-3)(a-5)

So now we have;
2(a-5)/(a-3)(a-5) (if we divide out the common factor (a-5), we get)
2/(a-3)