1888888888888888888777754%&-76$$
Answer:
8 centimeters.
Step-by-step explanation:

Divide 3 both sides:

Multiply 4 on both sides:

8cm on the map represents 20km.
3(y-1)=y-11
Distribute:
3y - 1 = y- 11
Add 11 to both sides
3y - 12 = y
subtract 3y on both sides
-12 = -2y
Divide by 2y
y= 6