Nick is training for a biathlon he will swim every 6 days and bicycles every eight days on what days will he both swim and bicycle

On every 24th day because 6 and 8 are both multiples of every 24th number like 24.
6×4=24 8×3=24
6×8=48 8×6=48
48/2=24
6×12=72 8×9=72
72/3=24 and it keeps going

So the answer is every 24th day Nick will both swim and bike.

First subtract 10 from both side
y^2+6y-16=0
(y+8)(y-2)=0
-8 and 2