Mr. X paid for a painting using currency notes of denominations 1$, 2$

This is a subtly difficult question. The question of what the price paid for the painting requires being able to determine exact number of each denomination used. We only know that at least one of each denomination is used and the total number of 10's and 5's used is one more than that of the total number of 2's and 1's. Stmt !) tellls us 13 total notes are used. Now we know that a total of 7 10's and 5's were used and a total of 6 2's and 1's. But, we cannot determine the exact number of each note used. Therefore, Stmt 1) is NOT SUFFICIENT. Stmt 2) tells us the price of the painting was a multiple of $10. Since wa can get a multiple of 10 several ways using the information we have (not including Stmt 1), this is NOT SUFFICIENT either.

Together Stmt's 1) and 2) tell us that Mr. X used 13 notes (7 -10's and 5's; 6- 2's and 1's) and that the total price paid was a multiple of $10. Thus, the question is can we come up more than one way to get a multiple of 10 using the above information. The test makers are begging us, at this point to pick answer choice C. But a bit of patience and work shows us that we can come up with a multiple of $10 several ways:
1) 3 - 10's; 4 - 5's; 4 - 2's; and 2 - 1's = $60
2) 5 - 10's; 2 - 5's; 4 - 2's; and, 2 - 1's = $70

Correct answer is E