You could set this up as a equation. Because there was a total of 26 you would for sure put =26. Next you are told Alvin has 8 MORE than Bali, therefore you would be adding the unknown value of Bala by 8. This could be represented as x+8=26. Now that you have x added to 8 you need to add another x to the equation to fully represent the problem since Alvin has 8 more stickers than Bala does. The new equation would become 2x+8=26.
You must now isolate x by first subtraction 8 from both sides which will leave you with 2x=18. Then you divide on both sides by 2 and will leave you with x=9