Problem
Add up the values: 6 hundreds is 600, 13 tens is 130, and 24 ones is 24. Combine them by carrying the extra tens and ones into the next place.
Place value lets me trade 10 ones for a ten and 10 tens for a hundred, which is core Grade 2 understanding of three-digit numbers.
2.NBT.A.1Organize Information In More WaysThe number described as 6 hundreds, 13 tens, and 24 ones is the same as 754.
The described number is nothing more than the value of its named parts put together: the 6 hundreds are worth 600, the 13 tens are worth 130, and the 24 ones are worth 24.
Hundreds, tens, and ones are separate names for pieces that together cover the whole number with no gap and no overlap, so their values add back to the whole.
Thirteen tens is worth 130 and twenty-four ones is worth 24 because a count of equal-size groups is that many copies of the group's size.
Adding 600 + 130 + 24 pushes the tens and ones past a single digit, so I trade ten ones for one ten and ten tens for one hundred until each place holds a single digit, leaving 7 hundreds, 5 tens, and 4 ones.
Now take 264 away from 754 to get the number that is 264 less.
Subtracting two three-digit numbers with regrouping is a Grade 3 fluency skill.
3.NBT.A.2Identify SubproblemsRead 490 as a count of tens: 490 is 49 groups of ten (with 0 ones left over).
Seeing 490 as 49 tens is just place-value reading, the same skill as knowing 490 has a 9 in the tens place plus 4 hundreds = 49 tens.
2.NBT.A.1Organize Information In More WaysTrade your tens and ones into neat place value, and reading 490 as 49 tens is easy Grade 3 sense!