Answer:
56 miles
Step-by-step explanation:
Let x is the total distance Sam will travel today
Sam has already biked 12 + x/4 miles
He needs to bike 3x/8 (x.3/8) + 9 miles
12 + x/4 + 3x/8 + 9 = x
21 + x/4 + 3x/8 = x
21 + 2x/8 + 3x/8 = x
21 + 5x/8 = x
21 = x - 5x/8
21 = 3x/8
21.8 = 3x
168 = 3x
x = 168/3
x = 56 (miles)
