Statement 1
$$k-m=7$$
$$k=m+7$$
$$jk-mj$$
$$j\left(k-m\right),\ where\ k=\left(7+m\right)$$
$$=j\left(7+m-m\right)$$
$$=j\left(7\right)$$
Value of J is unknown
Hence, statement 1 is NOT SUFFICIENT.
Statement 2
j=11
$$=jk-mj$$
$$=j\left(k-m\right)\ where\ j=11$$
$$=11\left(k-m\right)$$
$$=11k-11m\ $$
value of k and m are unknow, hence statement 2 is NOT SUFFICIENT.
Combining both statement together
From statement 1 k-m=7 and k=7+m
From statement 2, j=11
From question statement,
$$jk-mj=j\left(k-m\right)$$
$$where\ j=11\ and\ k=7+m$$
$$11\left(7+m-m\right)$$ $$11\left(7\right)=77$$
Both statement together are SUFFICIENT $$answer\ is\ Option\ C$$
