Correct this value using find() in Vue.js

#1 
    console.log(this.tiles.find(this.findStart))

returns expected results using this code:

    findStart: function (value) {
      var x = 5, y = 10;
      return value.x === x && value.y === y
    },

but not this code:

    findStart: function (value) {
      var x = this.room.startX, y = this.room.startY;
      return value.x === x && value.y === y
    },

How do I pass the correct “this” value to the second set of code?

#2