this is a case of plugging the given values into the given equation.
The equation we are given is V=lwh where
V = 550
l = 10
w = ?
h = w + 1
When plugged in this looks like

Divide both sides by 10

Leaving us with

at this point i would just check and test number that when multiplied by 1 unit more, it equals 55, I got somewhere between6.9 and 7.9 to 7 and 8 depending on how you are allowed to round.