Question

please solve 11th question

Answer 1

7×11×13+13 may be written as, 13x{(7x11) + 1} i.e. 13x(78). So other than 1 and the number itself, 13 and 78 are also the factors of the number. Further, 78=39x2. So, 39 and 2 are also it's factors. So this number is definitely not prime. Hence its composite number

Answer 2

as it is a product of prime number
therefore it is divisible by many other numbers
therefore it is a composite number