Question 46991
If the problem is (a+3)(a+4)=72,on expansion it gives 
a^2+7a+12=72
a^2+7a+12-72=0
a^2+7a-60=0
On factoring, we get
(a+12)(a-5)=0
So,either a+12=0 or
a-5=0
Therefore, a=-12 or +5