Let's build the equation counting how many x's and 1's are there on each side.
On the left hand side we have 5x's and 8 1's, for a total of 
On the left hand side we have 3x's and 10 1's, for a total of 
So, the equation we want to solve is

Subtract 3x from both sides:

Subtract 8 from both sides:

Divide both sides by 2:

First you cross multiply.
2*(b-4)=6b
Then distribute the 2.
2b-8=6b
Minus 2b from each side.
-8=4b
Divide each side by 4.
-2=b
So -2 is your answer.
Answer:
ALL CAN BE MADE IN SOLID FIGURES