You would subtract f(x) from both sides g(x)-f(x)=k
Check the picture below.

since the width is just a dimension unit, it can't be -31.
what is the length? well, the length is w + 30.
Pi x Radius squared should be your answer.
hurdler falled down before the 353535 steps of 100100100 race.
we need to find where she fell down
so we need subtract 353535 from 100100100

she falled at 99746565 step before completing the race
Function because nothing repeats in the domain