What is the right way for an older sister to deal with a younger brother?
My older children sometimes helped the younger ones do their homework.
First of all, teach him to be independent. Do not sit next to him while he is writing the assignment, just ask to bring it for review. If you don't understand something, explain it, but don't do it instead.
If you see that he solves some tasks slower and worse, let's give additional ones of the same type.
Also explain to him why he needs to learn. That assessments are not so important as knowledge.
Do not scold him for poor grades, but force him to go through the topic again and understand what he missed.
Encourage him in every way, praise him for good grades, come up with some small awards.
It can be a movie or a cartoon that you watch together. Go to a park or museum together.
The older he gets, the more difficult it will be.
Do not try to replace his parents, it will not be any better for him or for you.
You are an older sister who is willing and able to help.
My brother and I also have a big difference of eight years.
When we were in school, he was also lazy to do his homework, asked for help to solve.
But I refused, because I knew - he did not delve into the essence of the assignment, I did not want to think for myself.
You cannot make concessions, otherwise, the material will not master the given, and then it will be even more difficult, since all educational material, especially the exact sciences, is based on knowledge of the previous material.
Boys are more fond of figurative explanations.
Therefore, ask him to draw a problem statement or use any materials at hand. Make it a game to keep your brother interested.
Cars or some other toys let the entrance to solve various educational problems.
Read with him interesting informative books on these topics, or maybe there are videos so that he can better assimilate the material.
You can occupy him with the development of memory, observation. It's also good.
For example, lay out several different objects, give time to memorize, and then remove some object, ask if everything remains in place.
My advice to you is to hire a tutor and let him work with him, after all you are not a parent to him, just an older sister, let him or herself delve into everything, and if you explain everything to him in a row, then he will grow up dependent, just leave him alone, yes and you will not always be there to help him with this.