Overview: 2 questions will be solved this time.Among them
           ☆1 inequalities
           ☆1 equations

[ 1/2Inequality]
    Assignment:Find the solution set of inequality 480 ≤600-4X ≤520 .
    Question type: Inequality
    Solution:
    The inequality can be reduced to 2 inequalities：
        480 ≤600 - 4 * x         (1)
        600 - 4 * x ≤520         (2)

---

    From inequality(1)：
         x ≤ 30
    From inequality(2)：
         x ≥ 20

---

    From inequalities (1) and (2)
         20 ≤ x ≤ 30    (3)

---

    The final solution set is :
         20 ≤ x ≤ 30
[ 2/2 Equation]
    Work: Find the solution of equation 1200+（8-12X） = 0 .
    Question type: Equation
    Solution:Original question:

1200

+

(

8

−

12

X

)

=

0

    Remove the bracket on the left of the equation:

Left side of the equation =

1200

+

8

−

12

X

=

1208

−

12

X

    The equation is transformed into :

1208

−

12

X

=

0

    Transposition :

-

12

X

=

0

−

1208

    Combine the items on the right of the equation:

-

12

X

=

-

1208

    By shifting the terms and changing the symbols on toth sides of the equation, we obtain :

1208

=

12

X

    If the left side of the equation is equal to the right side, then the right side must also be equal to the left side, that is :

12

X

=

1208

    The coefficient of the unknown number is reduced to 1 :

X

=

1208

÷

12

=

1208

×

1 12

=

302

×

1 3

    We obtained :

X

=

302 3

    This is the solution of the equation.

    Convert the result to decimal form :

X

=

100.666667

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