Answer:
x=9
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