What is the value of jk - mj?

[BTGModeratorVI]

What is the value of jk - mj?

(1) k - m = 7
(2) j = 11

Answer: C
Source: Economist GMAT

[deloitte247]

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 $$answer\ is\ Option\ C$$

[Brent@GMATPrepNow]

What is the value of jk - mj?

(1) k - m = 7
(2) j = 11

Answer: C
Source: Economist GMAT

Target question: What is the value of j(k - m)?

Statement 1: k – m = 7
If k - m = 7, then j(k - m) = j(7).
Since we don't know the value of j, we can't answer the target question with certainty
Statement 1 is NOT SUFFICIENT

Statement 2: j = 11
If j = 11, then j(k - m) = 11(k - m)
Since we don't know the value of (k - m), we can't answer the target question with certainty
Statement 2 is NOT SUFFICIENT

Statements 1 and 2 combined
k - m = 7 and j = 11, then j(k - m) = 11(7) = 77
So the answer to the target question is j(k - m) = 77
Since we can answer the target question with certainty, the combined statements are SUFFICIENT

Answer: C

Cheers,
Brent