Isometry (iso meaning same and metry meaning measure)
preserves the length and overall mass/size of a shape during a transformation. The 3rd option is the only shape that changes size in the examples, making it a non isometric transformation.
anyhow, to get the "recurring decimal to fraction", you start by setting to some variable, "x" in this case, then move the repeating part to the left of the point by multiplying it by some power of 10, and then do the equating.