If a = x+21, b = 4, c = x + 3, and d = 10, then the value of x =

Using the intersecting chord theorem:
a x b = c x d
x+21 * 4 = x+3 * 10
Simplify:
4x+84 = 10x+30
Subtract 30 from both sides:
4x + 54 = 10x
Subtract 4x from both sides:
54 = 6x
Divide both sides by 6:
x = 9
Answer:
x=9
Step-by-step explanation:
(segment piece) x (segment piece) = (segment piece) x (segment piece)
ab = cd
(x+21) *4 = (x+3)*10
Distribute
4x+84=10x+30
Subtract 4x from each side
84 = 10x-4x+30
84 = 6x+30
Subtract 30 from each side
54 = 6x
Divide by 6
54/6 = 6x/6
9=x