When we subtract  from a two digit number, the only number that changes in our answer is the tens position, and it will always go down by . Mentally, we can subtract  from the number in the tens place to find our answer. 

When we subtract  from a two digit number, the only number that changes in our answer is the tens position, and it will always go down by . Mentally, we can subtract  from the number in the tens place to find our answer. 

When we subtract  from a two digit number, the only number that changes in our answer is the tens position, and it will always go down by . Mentally, we can subtract  from the number in the tens place to find our answer. 

This is a subtraction problem because Lisa has alreayd gone to some of the parties that she was invited to, so she has less parties left to go to than she started with this summer. 

We can start at  and count back .

This is a subtraction problem because we want to know how much longer the dog is compared to the cat, or the difference between their lengths. 

This is a subtraction problem because we want to know how many desks are left over after all of Mr. Bell’s class sits at a desk. We take the number of desks in his room, and subtract the number of students that he has. . 

This is a subtraction problem because we want to know how many goldfish the pet store has left over after the teacher buys the first and takes them away from the store. We take the number of goldfish that the store had and then subtract the number that the teacher bought. .

To solve this problem, we first have to find our unknowns. Our unknowns are the number of flyers that she hung on the west side of the building and the number of flyers she has left over. We can set up equations for these unknowns by letting  represent the flyers she hung on the west side and  represent the flyers that she has left. 

  because she hung half as many flyers on the west side as she hung on the east side. When we half something we always divide by .

To find the total number of flyers that she hung we add the amount of flyers on the east side and the amount on the west side. 

To find how many flyers she has left, we subtract that total flyers that were hung from the  flyers that she started with. 

To solve this problem, we first have to find our unknowns. Our unknowns are the number of flyers that she hung on the west side of the building and the number of flyers she has left over. We can set up equations for these unknowns by letting  represent the flyers she hung on the west side and  represent the flyers that she has left. 

  because she hung half as many flyers on the west side as she hung on the east side. When we half something we always divide by .

To find the total number of flyers that she hung we add the amount of flyers on the east side and the amount on the west side. 

To find how many flyers she has left, we subtract that total flyers that were hung from the  flyers that she started with. 

Megan has  of water, but she needs . To find out how much more she needs we subtract.