5y-6=3y-20 how do i solve this problem

In a graph with several intervals o data how does a constant interval appear? what type of scenario produces a constant interval?

Can someone check if i did this correct. it’s number 4 if you’re wondering.

In 2009, there were 1570 bears in a wildlife refuge. in 2010, the population had increased to approximately 1884 bears. if this trend continues and the bear population is increasing exponentially, how many bears will there be in 2018?