-6x + 10 is the answer!!!!
Subst for f and t in...
9t+3ft+12 = 9×21 + 3×3×21 + 12 = 390
Using linear pairs,

By the exterior angle theorem,

50 miles = 1 hour
50 x 1 = 50
a. 50 miles x 2 hours = 100 miles
b. 50 miles x 4.3 hours = 215 miles
c. Converting minutes to hours, it would make 20 minutes become 0.333 hours.
50 x 0.333 = 16.65 miles
I don’t know the gap at the beginning but the answer is c