Answer: 
Step-by-step explanation:
Given the equation
you need to solve for the variable "b".
You need to apply Distributive property on both sides of the equation:

Now you need to add 21 to both sides of the equation:

Subtract
from both sides:

And finally, you can divide both sides of the equation by 18:

Answer:
c y=20x
Step-by-step explanation: