you would follow the order of operations
Parentheses
Exponents
Multiply/Divide
Add/Subtract
if it is multiply or divide, go from left to right. do the same if it is addition or subtraction
4000/10x2+4-8
first, do 4000/10
400x2+4-8
then do 400x2
800+4-8
then do 800+4
804-8
796
rounding to the nearest tens would make it 800
because 9 rounded up is 10