B=6 i believe! if you use the pythagorean theorem (a^2+b^2=c^2) then you should be able to turn 8^2 and 10^2 into 64 and 100, respectively. 100-64=36 and the square root of 36 is 6. you can plug it in by calculating 8^2 + 6^2, which equals 100! hope this wasn't too confusing XD
