頑皮的貝殼把數字藏起來了！
A naughty seashell hid the number! 🐚
頑皮的貝殼遮住了算式裡的數字：7 + ? = 12。這類「求未知數」題目是代數思維的萌芽 — 小朋友要理解加減互逆的關係，用「12-7」或者「由7數上去」找出答案。小一面試的填充題（fill in the blanks），考的正是這種能力。
A mischievous seashell hides a number in the equation: 7 + ? = 12. These "find the unknown" problems are the seeds of algebraic thinking — children use the inverse relationship between addition and subtraction, solving with "12−7" or by counting on from 7. Primary One interview fill-in-the-blank questions test exactly this.
用實物演示：「7粒貝殼，要湊夠12粒，還要多少粒？」兩個方法都鼓勵嘗試：數上去（counting on）與直接減法，讓小朋友自己比較哪個方法快、為什麼快。
Demonstrate with real objects: "7 shells — how many more to make 12?" Encourage both methods — counting on and straight subtraction — and let your child compare which is faster, and why.
玩「我想著一個數」謎語：「我想著一個數，加4之後是9，你猜是多少？」由10以內開始慢慢加深。調換角色、由小朋友出題考你，理解會更加深。
Play "I'm thinking of a number": "I'm thinking of a number; add 4 and you get 9 — what is it?" Start within 10 and build up slowly. Swap roles and let your child set the riddle — understanding deepens when they teach.