Practice time P seconds
Timing in the Race : R = 58.4 seconds
Improvement Record I = 2.6 seconds
Race timing = Practice timing - Improvement record
R = P - I
58.4 seconds = P - 2.6 seconds
Take 2.6 seconds to the left hand side, 58.4 sec + 2.6 sec = P
P = 61.0 seconds
Now, subtract improvement record time from Practice time, you get the race time.
