I think A,
Given - Brandon's compensation is structured so that each month he earns a $5000 base salary plus 10% of his total sales above $10000 for the month.
If we assume brandons sales figure as x for any month the equation we will able to form for total compensation is like below.
Total compensation = $5000 + 0.1 (x-$10000) -- (eq1)
lets find Brandon's total sales for the month of August using given conditions.
1st - Had Brandon sold $10000 more than he did in August, his total compensation for the month would have been equal to 15% of his sales.
Therefore equation will be form like,
brandon new sales figure will be = x + $10000
$5000 + 0.1 (x + $10000 - $10000) = 0.15 ( x + $10000)
5000 + 0.1x = 0.15x + 1500
3500 = 0.05x
x = 350000/5 = $70000.. Hence Sufficient.
2nd - Had Brandon sold $40000 less than he did in August, his total compensation for the month would have been equal to 10% of his sales.
Therefore equation will be form like,
brandon new sales figure will be = x - $40000
$5000 + 0.1 (x - $40000 - $10000) = 0.1 (x - $40000)
if you see 0.1x will get cancelled on each side so there will be no solution.. Hence Not sufficient.
Answer A.