Given that a and x are integers, a > 1, a|(7x +2) and a|(28x +11), find a. Solution we notive that 7x+2 and 28x+11 have a as common divisor i.e. we have to find x such that the gcd of 7x+2 and 28x+11 is greater than 1 Also 28x+11 = 4(7x+2)+3 hence 3 could be gcd if 3 divides 7x+2 which is possible for x=1 Hence a=3 in which case x=1.