So PEMDAS is order of operations basicly.
P=Parenthesis
E=Exponets
M=Multiplication
D=Division
A=Addition
S=Subtraction
For example: 2x4+(9x9)-1
When solving order of operations you ALWAYS start with the problem in the parentheses.
(9x9)=81
Now multiplication comes next so, 2x4=8
Then addition, 8+81=88
Lastly subtraction, 88-1=81