Question 879348
Take 40% of $210 to get 


0.40*210 = 84


They want to make a profit of $84. Add this amount onto the initial cost: 210+84 = <font color="red">$294</font>


So they need to sell it at <font color="red">$294</font>. 


Since they said that's wrong, there is either a typo in the original question or in the answer (or maybe the computer is misreading). Also, be sure to write "S=210+.40(210)" and NOT "S=210-.40(210)". Notice how there's a plus sign in the correction.