Question 178253
Let the number of subway fares be s
Since the total monthly cost without the coupon book should equal the total monthly cost with the coupon book 
Then  s(1.55)   =   s(.95) + 12
1.55s    =   .95s  +  12
.6s    =    12
s     =    20


Therefore, the number of subway fares in order for the total monthly cost without the coupon book to equal the  total monthly cost with the coupon book is 20.


Checking:
Total monthly cost without the coupon book:	 20(1.55)       =   $31.00 
Total monthly cost with the coupon book:	 20(.95) + 12   =   $31.00