In math x, y, n, or any other letter stands for a variable. A variable is an unknown quantity that represents some actual number (or numbers), but we often don't know what it is yet.
In an equation, both sides of the equal sign represent the same number, once all the math is done. So saying n/33 = 19 is the same as saying 19 = 19; we just don't know yet what number n divided by 33 equals 19.
An equation is like a see-saw: if an extra person gets on one side, then someone who weighs the same has to go on the other side to keep the see-saw level. So you can add, subtract, multiply, or divide any number to one side of the equation as long as you do the exact same thing to the other side.
So, to solve for n in n/33=19, we want to get n all alone on one side.
n/33 = 19
33*n/33 = 19*33 Multiply both sides by 33
1*n = 627 33 divided by 33 equals 1
n = 627
And you can check: n/33 = 19 --> 627/33 does equal 19