Trible for loop Time Complexity, Help!

it’s a example in our data structure class
I really can’t think step by step how this code works…
my brain hurts…
like the more I think i just got more confused…

var n = 10;
var x = 0;
for(var i=1;i<=n;i++) {
  for(var j=1;j<=i;j++) {
    for(var k=1; k<=j; k++) {
      x = x + 1;
    }
  }
}

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