Answer: 2 training sessions
How:
With the info given, you create the equation...
35x + 30 = 25x + 50
The first thing you would do is subtract 25x from both sides since it’s the lesser value, giving you...
10x + 30 = 50
After that, you want to isolate the 10x by subtracting 30 on both sides, giving you...
10x = 20
The last thing you would do is divide both sides by 10 in order to completely isolate the value, giving you your final answer of...
x = 2
In other words, this means it would take 2 training sessions for both the gyms to reach equal value in a month.