BEDMAS is a word to help you to remember what to do first in a calculation involving more than one operation.
BEDMAS means:
Brackets: 
Work out the value of any expressions inside brackets. 
Exponents: 
Work out the value of any numbers or expressions with exponents or indices. Sometimes shown as 'of ' meaning multiply. 
Division Multiplication 
If these two operations occur together, work from left to right. 
Addition Subtraction 
If these two operations occur together, work from left to right. 
Calculate: 

a. 3 + 4 × 5 
a. 3 + 4 × 5 = 3 + 20 = 23 
b. 4 + (6 − 2) 
b. 4 + (6 − 2) = 4 + 4 = 8 
c. 13 − 2 × 5 + 4 
c. 13 − 2 × 5 + 4 = 13 − 10 + 4 = 7 
d. 3 × 6^{ 2} 
d. 3 × 6 ^{2} = 3 × 36 = 108 
Care should be taken when using a calculator to do calculations of this type.