After the 15% discount, Maria pays 85% of the cost. That cost is the sum of the fixed cost and the variable (per visit) cost.
... (updated cost) = 0.85×($150 +$30×a)
... (updated cost) = 127.50 +25.50a . . . . in dollars
To round to the nearest hundredth is 42.66
Do you mean 90(3n-6) if so the answer is -270 but if you mean 3n-6 the answer is -3
