Question

find the largest number that will divide 398,436and542 leaving remainders 7,11and15 

Answer 1

Let that number be  X.      Let n1 , n2  , n3 be some +ve numbers

   398 =  X  * n1 + 7      =>  391  =  X * n1    => X * n1 = 17 * 23
   436  = X *  n2 + 11    =>  425  =  X * n2    =>  X * n1  = 17 * 25
   542  =  X * n3 + 15          527  = X * n3          X * n3  = 17 * 31

X = 17

Answer 2

we can write this 398-7=391 436-11=425 542-15=527 these all no. are divided by 17 with remainhng reminder 7 11 15