4 + 4 / 5 b = 9 / 10 b

Step-by-step explanation:

The first step is getting 4 on the other side so you minus 4 to get 4/5b=9/10b

you then subtract 9/10 from 4/5 in order to do this you need to get 4/5 a denominator of 10, so you take 4/5 times 2/2 to get 8/10

So now you can take 8/10-9/10=-1/10

You now have - 1/10b=-4

you then times - 10 on both sides to get b by itself

b = - 4 * - 10

b=40