Combining like terms means, simply, to combine all the numbers that have the same letters with them.
5x and 6x both have the letter x. Let's combine them! 5x+6x = 11x
y, y, and 3y all have the letter y. You can imagine y to be 1y, they're the same.
1y + 1y + 3y = 5y
4, 6, and 2 don't have any letters. 4 + 6 + 2 = 12
Now you have to put all the final terms together to get: 11x + 5y +12
