The 4 integers j,j,k and n have an average of 0. which of the following equations must be true ?

Let m and n be 2 positive integers, such that m < n . Which of the following compound inequalities must be true?

If r=i+j+lamda(2i+j+4k) and r.(i+2j-k)=3 are the equations of a line and a plane respectively then which of the following is true?

Let s_1 = {(i,j, k) ∶ i,j, k ∈ {1,2, … ,10}} , s_2 = {(i,j) ∶ 1 ≤ i s_3 = {(i,j, k, l) ∶ 1 ≤ i s_4 = {(i,j, k, l) ∶ i,j, k and l are distinct elements in {1,2, … ,10}} . If the total number of elements in the set s_r is n_r , r= 1,2,3,4, then which of the following statements is (are) TRUE ?