The answer is 133 beats per minute.
To calculate this, we will use proportion.
If 190 beats per minute are 100%, how many beats per minute are 70%:
190 bpm : 100% = x : 70%
\(\frac{190 bpm}{100} = \frac{x}{70}\)
\(\frac{70 * 190bpm}{100} = x\)
\(x = 133 bpm\)
Thus, Xanthe's target heart rate is 133 beats per minute.
