18: 2 Page, ABE plane corresponds to EF, BD and AC respectively, and is derived from the last two cubes.

Step 3 draw it yourself

4. It consists of at least six cubes.

Page 19: 1, which is surrounded by four faces, the faces intersect with six straight lines, and the straight lines intersect with curves.

2 1 ratio 3, 2 to 2, 3 to 1

3. The first one can't be a prism, the second one can be a triangular prism and the third one can't be a prism.

4. They are heptagon, rectangle, trapezoid and rectangle respectively.

5, can be rectangular and square.

6, subtract the third square in the second column.

7. Draw it yourself

8, ditto

9,7-4 = 3m6 divided by 2=3M.

3. 14 times the square of 3 times 1/3 times 3 =28.26 cubic meters.

Cubic quadratic 3. 14 times 4= 1 13.04 cubic meters.

28.26+113.04 =141.3 m3.

10, which can be an inverted triangle, quadrilateral or pentagon.

1 1, irregular figure

Page 25: 1, (1) is marked as -3 degrees Celsius (2), moving 2 cm to the east, and the stationary mark is 0.

(3), recorded as-3.8t..

2, a set of positive numbers: 3, 5.6, 15, one ninth.

A set of negative numbers: -7, -2/3, -8 and 1/4.

Integer set: 0, 3, -7, 15

Score setting:-two thirds,-eight and a quarter, one ninth, 5.6.