Answer:
45.71 - 6x
Explanation:
If Heather bought markers to donate, the amount she donates is subtracted from her balance of 45.71. We know she bought 6 packs of markers, but we do not know how much each pack cost. We will make this our unknown "x". The expression for packs of markers costing "x" is 6x. Because she buys them from her account, which takes aways from her balance, the expression that represents this donation is:
45.71 - 6x
(Notice that the question asks for the EXPRESSION after she buys the markers, not the EQUATION. The difference between an expression and an equation is the lack of an equals sign in the expression.)