Multiplication scales faster than addition. You're not just adding the last number, you're adding an additional count of the first number.
5 x 5 is a shortcut to writing 5 + 5 + 5 + 5 + 5
So, if x is 1:
5(1)+1 = 5 (times nothing really) + 1 = 6
4(1)+2 = 4 (times nothing again) + 2 = 6
If x is 2:
5(2)+1 = 5 + 5 + 1 = 11
4(2)+2 = 4 + 4 + 2 = 10