Problem
Mia picked 4 more than Emma's 7, so 11 strawberries.
'How many more' means add the difference to the known count. Adding 4 to Emma's 7 gives Mia's count directly.
Identify Subproblems2.OA.A.1Total 35 minus Mason's 9 and Emma's 7 leaves Mia plus Hana: 19.
The total 35 is exactly the four counts added together. Taking the two known rows (Mason 9, Emma 7) back out undoes that addition, leaving only Mia and Hana's combined count.
2.MD.D.10Identify SubproblemsTaking Mason's 9 and Emma's 7 away from the total 35 leaves exactly Mia and Hana's counts added together.
The total 35 is just the four people's counts added up, so it is made of exactly those four parts.
Every strawberry in the total belongs to one and only one of the four people, so the four counts fill the total with no gaps and nothing counted twice.
Because the total is those four parts added, taking the two counts you already know back out leaves the two counts you don't.
Taking a number away cancels having added it, so subtracting Mason's 9 and Emma's 7 undoes adding them and only Mia's and Hana's counts remain.
19 minus Mia's 11 leaves Hana with 8.
Subtracting the already-found Mia (11) from the Mia-plus-Hana total (19) works backwards to Hana's count alone.
Work Backwards2.OA.A.1A table's total is the sum of its rows. Subtract what you know and the unknown rows' sum remains — work backwards to find each one.