What is the value of x?

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x=

A^2 + b^2 = c^2
6^2 + b^2 = 10^2
36+b^2 = 100, then i would subtract 36 on both sides to isolate the b^2, the value we're trying to find.
b^2=-36+100
b^2 = 64, now we have to find the square root of 64...
b(x)=8

The answer would be 24mm

The year before the 10s so it was like when caveman were alive