I guess you mean: evaluate the expression 4y-(3+y) when y=2? You work out the contents of the brackets first: 3+y is 3+2=5; then the expression becomes 4y-5; multiplication has priority over subtraction so substitute y=2 in 4y (4 times y) and you have 4*2=8, making the expression 8-5; finally, do the subtraction 8-5=3. This is an illustration of order of operations: brackets (parentheses) first, then multiplication and division, then addition and subtraction.