Runescapedude, do not use your fingers! Use a number line. You can take yourself through the calculation and see where the expression, 3-7+2, will be on the number line.
Young students in grade 1 usually learn to add and subtract whole numbers both on a number line and on their fingers. At that grade level, the number line starts at zero, and counts upward to the right. Those students in grade 1 only use whole numbers, and they are only the positive numbers.
Now that you are learning to subtract larger numbers from smaller numbers, you need to extend the number line toward the left of zero to use the negative numbers.