if she wishes to buy a <u>maximum</u> amount on cloths then the sign will be is less than or equal to (≤) because of the word maximum. next you will divide 400 by 1/2.
Note that the graph is shaped like a V. The left half of the graph is decreasing from -∞ up until 0 when it hits the origin and starts to increase. Put this into interval notation: (-∞,0).