Divide both sides by the square root of 2. If you are looking for an exact answer that is rationalized, it would be found by multiplying 6/sqrt(2) * sqrt(2)/sqrt(2) to get
Divide 6 by the square root of 2 to get the value of b. The exact answer would be left: 6 divided by the square root of 2. I got an approximate number of 4.255