Both answers can't be right or we'd always be arguing about the answers to math problems. The nice thing about math is that there's always just ONE answer!
So, a long time ago, math geeks decided to make a set of rules for what to do first in a math problem.
These rules are called "the order of operations."
I'll tell you what the rules are in the next lessons... For now, remember this word:
Go to the next lesson to find out if the answer to our problem is 7 or 9! And go all the way through to find out what all the letters of PEMDAS stand for!