The answer is -8 and 8 and anything in between them. So 5 and -3.
First I subtracted 68 and made it into an equation. So x^2-64=0 then you factor it into (x+8)(x-8)=0
then put -8 and 8 on a number line with closed dots above them (because it's greater than or EQUAL to, so -8 and 8 are already answers.) then take a number that's greater then -8 (I used -9) and sub it into the original equation. You'll get 81 which doesn't work because 81 isn't greater than or equal to 64. Then plug in 0 (it works) so any numbers in between -8 and 8 are in the solution. Lastly plug in 9 and it doesn't work. So your solution is -8, 8, and every number in between.