**Answer:**

1. x= 20/3 or 6.6666 repeating

2. x=3

3. a=39

**Step-by-step explanation:**

1. subtract 25 by 5 to get 20, then divide 20 by 3 to get x

2. divide 7 by 21 to get x

3. add 8 to 31 to get a equals 39

**Answer:**

17 degrees

**Step-by-step explanation:**

A. Area of a square= side length squared

=> A= (x-3)^2

= x^2-6x+9

b. Area of rectangle= larger side length* smaller side length

=> A= x(x-5)

= x^2-5x

c. If both areas equal then expressions for areas equal as well.

x^2-5x= x^2-6x+9

=>x=9

**Answer:**

**Step-by-step explanation:**

**big rectangle**

3 * 4 = 12 mm²

**little rectangle**

1 * 6 = 6 mm²

**triangle**

[(6-3) * 4] : 2 = 6 mm²

**sum the results**

12 + 6 + 6 = 24mm²

The answer is 6.601, and therefore, the second option.