(1)23-17-(-7)+(-16) (2)123×80%=x×(1+10%) (1)23-17-(-7)+(-16) (2)123×80%=x×(1+10%) (3) 1 - (1-0.5) △ 3 × [2 - (- 3) power]

(1)23-17-(-7)+(-16) (2)123×80%=x×(1+10%) (1)23-17-(-7)+(-16) (2)123×80%=x×(1+10%) (3) 1 - (1-0.5) △ 3 × [2 - (- 3) power]

(1)23-17-(-7)+(-16)
=23-17+7-16
=23-10-16
=13-16
=-3
(2)123×80%=x×(1+10%)
123×0.8=1.1x
123×8=11x
11x=984
x=984/11
(3) 1 - (1-0.5) △ 3 × [2 - (- 3) power]
=1-0.5÷3×[2-9]
=1-1/2÷3×(-7)
=1+1/2÷3×7
=1+1/2×1/3×7
=1+7/6
=13/6

The mathematics problem of hjaskf sky
Fill in the blanks
If the square root of the root sign a is positive or negative 2, then a = (), if the square root of a positive number is 2x-1 and - x + 2, then x = (), the positive number is ()

If the square root of a equals plus or minus 2, then a = (16)
If the square root of a positive number is 2x-1 and - x + 2, then x = (- 1), the positive number is (9)

1. Choose one
1、 A cuboid of 4cm in length, 1cm in width and 1cm in height is built into four cubes, and the sum of the surface area is increased by () cm
A.8 B.6 C.3
2、 The length, width and height of a cuboid are a, B and C respectively. If the height is increased by 2 meters, the volume of the new cuboid will be increased by () cubic meters
A.2ab B.2ac C.ab×（c+2）
3、 The edge length of a large cube is twice that of a small cube, so the surface area of a large cube is () of a small cube
a.4 b.4 c.12 d.6
Completion
Cut the 3 meter long wire into 5 sections, each section is () m long, and each section is () of the whole length
The unit of fraction is one fifth and the minimum band fraction is ()

1、c
2、a
3、b
Each section is 0.6 meters long, and each section is 1 / 5 of the total length
The minimum band fraction is 1 and 1 / 5

Figure 7
In rectangular ABCD, BF ‖ De, ad = 12cm, ab = 7cm, AE: EB = 5:2, then the area of quadrilateral ebfd is () (brief steps)

AE:EB=5:2
AB=7
So AE = 5, be = 2
AD=12
So the area of the right triangle adequate = 5 * 12 / 2 = 30
BF parallel De, ad parallel BC
So angle ade and FBC are equal or complementary
They are all sharp angles, so they are equal
AD=BC
Then right triangle ade and CBF are congruent
So the triangle CBF area is also 30
The rectangular area = 12 * 7 = 84
So the area of ebfd is 84-30 * 2 = 24cm & sup2;

The speed ratio of a, B and C is 3:4, and the speed ratio of B and C is 5:4

The speed ratio is 3:4 = 15:20
The velocity ratio of ethylene to propylene is 5:4 = 20:16
So the speed ratio of the three is 15:20:16