Add two whole tens and two 1-digit numbers

Students can add the two whole tens first (since they are multiples of ten), then add the two 1-digit numbers, and finally combine the two partial sums for an efficient calculation.

Because addition order doesn't matter, students learn they can rearrange and regroup the four addends in whatever way is easiest, demonstrating both the commutative and associative properties in action.

Both approaches are valid — the structure of the problems (tens separate from ones) makes mental addition accessible, but writing partial sums is also a useful strategy for students still building fluency.