Anyone know how to do problems 5-8?

Finding zeros or setting y ot f(n) equal to zero
 
and all you have to do is factor it, hoping you know how to do this

5. 0= n^2-2n-15
(n-5)(n+3)= 0
n-5= 0              n+3=0 
n=5 and n=-3

6.t^2+6t=27
t^2+6t-27=0
(t + 9) (t-3)= 0 
t=-9 and t=3

7. x^2-9x=-18
x^2-9x+18=0
(x-6)(x-3)= 0 
x=6 and x=3

8. a^2 - 7a = 30

a^2 - 7a -30= 0
(a-10)(a+3)=0
a=10 and a=-3

hope that helps

Ithink number to is 1 inch=5 miles