Math: Place Value is an abstract concept that can be difficult to understand. You can help your child identify the Ones position by having them use their finger to cover all but the last digit in a number. The digit shown is the Ones. If they use their finger to cover the Ones number they found, the next digit is the Tens. At his point in the text we are only working on Ones and Tens, so when they see a three digit number like 120 although it is 1 - Hundred, 2 - Tens and 0 - Ones, it is also correct to say that there are 12 - Tens and 0 - Ones.
Double Digit Addition & Subtraction: I have the students lay every problem out vertically unless it is provided that way. Each problem should be written like this:
12 32 +16 - 12 28 20
Remind them: We always start adding or subtracting on the right or the ones place.
Some students like to use a T-Chart where you draw a line down the middle and label the tens and ones, that is great since place value plays a role in problems that require regrouping (what you may call carrying) like this:
42 72 +18 -24 60 28
Having them lay the problems out vertically and reminding them that we always start in the ones place will help them master this skill.