Its simple really, I'm assuming theres a box of points, so look at your box. Points will be labled as such example (3,5), You would have to plot those two points on the graph. Remember when plotting, your first number is your X axis. So you would go to the number three on the line in the middle (Not -3) and your Y axis is your last number, so you would look at the line that is in essence cutting the graph in half, and plot the number 5. (Not -5).
If she gets 3% of what she sells you multiply the decimal form of the percent by the amount she has made: 50*.03=1.5 So she make $1.50 for every $50 of sales, so you multiply the amount she made by her commission each day by the number of days she worked: 1.5*30=45