There is only one way to reduce two layers in Ps: in the layers, click to select the layer to be reduced. Press Ctrl+T on the keyboard, and then pull the border inward to reduce it. If you want to keep the original scale unchanged, you can hold down Shift and then use the mouse to pull the border.
Select the layer that needs to be resized, and then use the Free Transform tool. Let's use PSCS6 to demonstrate the operation method: As shown below, to adjust the size of a layer, click to select it first (it can only be edited after it is selected).
Select this layer first, then press ctrl+T, and you will find an adjustment box around the picture. If you want to make the picture scale evenly, hold down the shift key and drag the adjustment box with the mouse to adjust it to the size you need, or directly enter a number in the property bar above to adjust the size.
Run PhotoshopCS5 to create a two-layer picture file. Here "layer 1" is blue, indicating that it is the currently editable layer. In order to change the size of Layer 2, you need to click Layer 2 with the mouse to make it an editable layer.