Answer: 1.85 + x = 5.30
Step-by-step explanation: If we know that Ethan planted a tree that was 1.85 meters tall from the start and several years later it's 5.30 meters tall, we know that something must have been added to the 1.85 in order to get 5.30 meters tall. Since we don't know what that value is, we can use x.
X is an example of a variable. A variable is just a letter that represents any number so in this case, it represents how much the tree has grown over a time period of several years.
So we can write this as 1.85 + x = 1.30.