Question

explain why (7*13*11+11) by (7*6*5*4*3*2*1+3) are composite number

Answer 1

By definition,

A composite number is a positive integer that has a factor other than 1 and itself. Now considering your numbers,

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.
Similarly, 7×6×5×4×3×2×1+5 can be written as 5x{(7x6x4x3x2x1)+1}, i.e. 5x(1009). So, other than the number and 1, it have 5 and 1009 as it's factors too. So it is also a composite number.

P.S. I am not professional mathematician. My answer is based on basic knowledge of mathematics.

Answer 2

7×13×11+11=11(7×13×1+1)=11(92)
and7×6×5×4×3×2×1+3=3(7×2×5×1×2×1+1)=
3(141)
because they have more than two factor hence they are composite number