Problem
July is 80 more than June, and June is 180, so July = 180 + 80 = 260.
Start from the value you already know (June) and apply the given step.
4.OA.A.3Identify SubproblemsJuly and August together make 640, so August = 640 - 260 = 380.
Knowing the total and one part, subtract to recover the other part.
4.OA.A.3Work BackwardsSubtracting July's count from the 640 July-and-August total leaves the number of frames made in August.
The 640 total is July's frames and August's frames added together, so those two months are the parts that build up that whole.
Only July and August go into the 640, with no month left out and none counted twice, so their two counts add back to the total exactly.
Taking July's count back out of the total reverses the adding that joined the two months, so what stays is the count that was added but never removed — August's.
Subtraction undoes addition, so removing an amount that was added leaves exactly the amount that was not taken out.
On the graph (each square = 20), July 260 sits 3 squares above 200, August 380 sits 4 squares above 300; join the points in order.
Converting the numbers into squares lets you place each point exactly.
5.MD.B.2Identify SubproblemsFill in what you can figure out first, then use the total to get the rest - then just plot!