Question 348690
Call the regular membership fee x.


If they take 10% off, then the reduced fee is 90% of the regular fee --> 0.9x


If you join on Monday, they take $20 off the reduced fee --> 0.9x - 20


So, if you pay $250 for joining on Monday, the equation is 


0.9x - 20 = 250



add 20 to both sides of the equation


0.9x = 270



Divide by 0.9 on both sides of the equation


x = $300 <==== ANSWER