Answer:
40 tarts
Explanation:
Lindsey had 400 tarts to start with, then she sold off 3/5 of them. Hence find the number of tarts left (2/5 of the original amount). Then she sold 1/4 of the remaining tarts. Therefore, find 1/4 or 2/5 of 400. The equation would be;
Now one just has to solve the equation;
40