Question

Q3 find the largest number which exactly divides 139 and 229, leaving remainder 4 in each case.

Answer 1

$139 - 4 = 135 \\ 229 - 4 = 225$
HCF(135,225) is that number
$225 = 135 \times 1 + 90 \\ 135 = 90 \times 1 + 45 \\ 90 = 45 \times 2 + 0$
so 45 is that number