Answer :

You want to use PEMDAS for this.
P= arenthesis ( )
E= xponents a²
M= ultiply ×
D= ivide ÷
A= dd +
S= ubtract -

What you want to do is go in order and ask yourself as you go.
Are there any ParenthesisNo
Are there any ExponentsNo
Is there any MultiplicationYes
Is there any DivisionNo
Is there any AdditionNo
Is there any SubtractionYes
Thats when you stop and you multiply what you have in the PEMDAS. Top to bottom. 3x5 which gives you 15Now you equation is 45-15. Thats when you subtract and you get your answer which is 30.