Sam's monthly earnings consist of a monthly salary and a 4 percent commission on the portion of her monthly sales that is in excess of $2,000. If Sam's monthly salary was the same in July as in August, how much greater were her sales in July than in August?
(1) Sam's monthly earnings were $3,620 in July and $3,580 in August.
(2) Sam's monthly salary was $3,500 in July and in August.
if S is the monhtly salary (constant in both months) then
3620=S+.04 (x-2000) ---1
subtract 1 and 2, and you get the diff between x and y which is the diff in sales --- suff
we dont know monthly earnings nor do we know monthly sales, -- insuff