to factor 18a, 20ab, and 6ab, first you'd have to figure out which variable could be factor-able between these three terms. since 18a does not contain a b, but all the terms of a, you can safely assume that a is factorable. next you have to find a number that is a common factor of 18, 20, and 6. we can begin from 6 since it's the lowest number, but since it isn't a factor of all three, the factor would not be six. as you count down the list and rule each out (5,4,3) the only number that is a common factor between all these terms is 2.
She makes $325 a week, so go to the 8th row, for weekly income of $300 to $400. She claims 2 exemptions, so go to the third column labeled 2. The value is 2. That means the $2 is withheld from her paycheck on top of the 6.25% for FICA. The total is therefore: