Question 305293
It's not an equation because there's no "=". 
It's an expression and all you can do is simplify it.
Factor the denominators, if possible.
{{{(2a+7)/(a^2-2a-15)-(3a-4)/(a^2-7a+10)=(2a+7)/((a-5)(a+3))-(3a-4)/((a-2)(a-5))}}}
{{{(2a+7)/(a^2-2a-15)-(3a-4)/(a^2-7a+10)=(1/(a-5))*((2a+7)/(a+3)-(3a-4)/(a-2))}}}