Answer:
4 hours
Explanation:
We can calculate this using the y=mx+c formula
y=total charge
m=per hour
x = (a) no. of hours
c= flat fee
y=20x+40
120=20x+40
We then solve like a normal equation
120-40=20x+40-40
80/20=20x/20
x=a
a=4
∴ Dalyn rents the boat for 4 hours