1, "add if you want to subtract" or "add and subtract if you want" is 8+7= 15, so 15-8 = 7, 15-7 = 8.

2, yuan+yuan angle+angle exceeds 10 angle, remember to change it to 1 yuan.

3. Plane graphics: square, rectangle, triangle, circle, parallelogram.

4. The units of RMB are (yuan), (jiao) and (min).

5. Two rectangles can form a big rectangle. (Two special rectangles can form a big square), and four cuboids can form a big cuboid.