Can someone me with #18 & #20?

Step-by-step explanation:

18)

If a quadrilateral is inscribed in a circle, the opposite angles add up to 180°.

Therefore we have the system of equations:

20)

If line AB is tangent to the circle, then the angle A is a right angle

Therefore the triangle is a right triangle. We can use the Pythagorean theorem:

Let O - center of the circle. Therefoe OA is the radius of a circle.

From a Pythagorean theorem:

56.6

step-by-step explanation:

the ratio of the perimeters is equal to the scale.

the ratio of the areas is equal to the square of the scale.

34 / 20 = k

a / 19.6 = k²

substituting:

a / 19.6 = (34 / 20)²

a = 19.6 (34 / 20)²

a ≈ 56.6

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step-by-step explanation: