Yobani,
You can set up the problem like this:
the variable can be anything you want the unknown number to be; in this case we'll call it "x".
6 times "x" increased by (plus) 17 is (equals) 19
so:
6x + 17 = 19
now, solve this algebraicly by solving for the "x"
first subtract 17 from both sides to get the 6x on one side, usually the left side, and we get
6x = 2
now, let's isolate the "x" on the left side by dividing both sides by 6 and we get
x = 2/6 factored down to 1/3
subsitute 1/3 for the x and let's see what we get
6(1/3) + 17 = 19
2 + 17 = 19, so we are right that x = 2/6 or 1/3