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People's education edition mathematics seventh edition
1.3((4-6)+ 10))

3(4-(6- 10)

3(4+( 10-6)

2+(- 13)-(-5)*7

[7+(- 13)×(-5)]÷3

(-5)×(- 13)-3×7=24

2. Suppose * * * has water x ml:

Drink 1/2 on the first day, and leave 1/2x.

Drink the remaining 1/3 the next day, that is,1/3 *1/2x =1/6x, leaving1/2x-1/6x =1/.

And so on: 1/4X is left on the third day.

So there is1/7x =1/7 * 5500 = 5500/7ml left on the sixth day.

On the tenth day,111x =111* 5500 = 500ml.

When his income is 100, it may be written as -240.

+500, -500 is 1000.

-600, +300 is 900.

Every change in revenue and expenditure 100 will change by 90 when bookkeeping.

4. A: The above conclusion is correct for the following reasons:

Let the number in the ten digits of this two-digit number be x and the number in the digits be y.

10X+Y+ 10Y+X

= 1 1X+ 1 1Y

= 1 1(X+Y)

X and y are integers.

So the sum of this two-digit number and the number transposed to this two-digit number must be divisible by 1 1.

5.2.2× 10^-2

6. Let the wind speed be X km/h and the aircraft speed be Y km/h when there is no wind.

Equations: 5.5(y+x)=30.

6(y-x)=30

Solution: x=5/22

A: The wind speed is 5/22 km/h. 。

7. let the degree of the first angle be x.

After cutting off its 1/3 at the first angle, it is complementary to the second angle.

The number of the second angle is 90-2x/3.

According to the first angle, make up 2/3 of it and make up the second angle.

The second angle is 180-5x/3.

Then 90-2x/3 = 180-5x/3.

X = 90,90-2x/3 = 30。

So: the first angle is 90 degrees, and the second angle is 30 degrees.