For number 25, you would plot 0 in the middle. then, plot the negative and positive numbers on the number line. It should be plotted like this, -4, -3, -2, -1, 0 1, 2, 3, 4. Monday would be -2, Tuesday would be -1, and Wednesday would be -3.
As for number 27, you can put zero represents the amount of money Monica started with.