If two secants intersect from a point outside of the circle, then the product of the lengths of the secant and its external segment equals the product of the other secant and its external segment.
#1
5(x+5) = 6(4+6)
5x + 25 = 6 * 10
5x = 60 - 25
5x = 35
x = 7
#2
4(x+4) = 3(5+3)
4x + 16 = 3 * 8
4x = 24 - 16
4x = 8
x = 8/4
x = 2
Remark
It's a right triangle so the Pythagorean Theorem applies. All you have to do is put the right things in the right places of the formula.
Givens
a = x
b = x + 4
c = 20
Formula and Substitution.
a^2 + b^2 = c^2
x^2 + (x + 4)^2 = 20^2
Solution
x^2 + x^2 + 8x + 16 = 20 Collect the like terms on the left.
2x^2 + 8x + 16 = 20 Subtract 20 from both sides.
2x^2 + 8x + 16 - 20 = 0
2x^2 + 8x - 4 = 0 Divide through by 2
x^2 + 4x - 2 = 0
Use the quadratic formula
a = 1
b = 4
c = - 2

From which x = (-4 +/- sqrt(24) ) / 2
x1 = (- 4 +/- sqrt(4*6) ) / 2
x1 = (- 4 +/- 2 sqrt(6) ) / 2
x1 = -2 + sqrt(6)
x2 = -2 - sqrt(6) This is an extraneous root. No line can be minus.
x1 = + 0.4495
x2 = x + 4 = 4.4495
Area of triangle = 1/2 ab sin c
Area of triangle = 1/2 (9.2)(11.9) sin (27)
Area of triangle = 24.85 ft²
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Answer: Area - 24.85 ft²
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You add all the sides together for perimeter
There are 6C3 = 20 such combinations.
abc, abd, abe, abf
acd, ace, acf, ade
adf, aef, bcd, bce
bcf, bde, bdf, bef
cde, cdf, cef, def