Find the common difference of an A.P if \( t_{18}-t_{14}=3 L \). If \( 3+k, 18-k, 5 k+1 \) are in A.P, then find \( k \). If \( p \) and \( q \) are positive integers, then we write \( p=a^{2} b^{3} \) and \( q=a^{3} b \) if \( a \), \( b \) are numbers, then verify that L.C.M of \( (p, q) \times \) H.C.F of \( (p, q)=p q \).