Verified Answer :

give the 2 numbers variables,say x and y.
then they multiply to -225.this means xy=-225
they add to 16.this means x+y=16
                                               y=16-x

substitute y=16-x onto xy=-225 to get x(16-x)=-225
then expand to get 16x-x^2=-225
rearrange to get a quadratic: x^2-16x-225=0
                                              x=(16+(16^2-4-225)^0.5))/2 or 
                                              x=(16-(16^2-4-225)^0.5))/2 


first you do -225+16 which equals -209

then you dived it by 2 which is not a whole number

then you go to 3 - no

4 - no

5 -no

6-no

7-no

8-no

9-no

10 - no

11 - yes    

so theequation is

11* (-19) +16 = -225