什么X的Y的: what's all this X and Y talk
【高141】口语格式 / fixed patterns
Tone colorsā tone 1á tone 2ǎ tone 3à tone 4a neutral
什么 + X + 的 + Y + 的，…… quotes two parallel or opposed categories only to wave them both aside, then states what really counts: 什么你的我的，都是大家的 (“no more ‘yours’ and ‘mine’: it all belongs to everyone”). 什么好的坏的，我们买的都是一样的。
X and Y are adjectives or pronouns made nominal by 的: 你的 / 我的, 好的 / 坏的, 新的 / 旧的, 老的 / 少的. After the comma comes the conclusion: all of it is shared, all of it is the same, or one criterion alone counts (能用就行). It is not a question: 什么 rejects the distinction, in a brusque tone, sometimes an affectionate one (a grandmother offering her savings).
Compare 什么X不X(的) (hsk5-g62), which waves away a single dimension (什么麻烦不麻烦的: “no need to make a fuss”), and 无论 / 不管……都…… (hsk3-g32), a neutral condition that keeps the categories (不管好坏，都要买). Here you do not say that the result is the same: you refuse the distinction itself. Register: spoken.
Sense taught here: the one shown by the two examples of the standard (GF 0025-2021, 高141), where the formula sweeps two categories aside and then gives the common truth.
Examples
什么你的我的，都是大家的。
Shénme nǐ de wǒ de, dōu shì dàjiā de.No “yours” or “mine”: it all belongs to everyone.
什么你的我的，这顿饭我请！
Shénme nǐ de wǒ de, zhè dùn fàn wǒ qǐng!Don't give me “yours” and “mine”: dinner's on me!
什么新的旧的，能用就行。
Shénme xīn de jiù de, néng yòng jiù xíng.New or old, who cares: as long as it works.
什么好的坏的，我们买的都是一样的。
Shénme hǎo de huài de, wǒmen mǎi de dōu shì yíyàng de.None of this good-or-bad talk: what we buy is all the same.
什么老的少的，进了这个门都得先洗手。
Shénme lǎo de shào de, jìn le zhège mén dōu děi xiān xǐ shǒu.Young or old, makes no difference: everyone who comes through this door washes their hands first.
Common mistakes
✗ 什么你我，都是大家的。 → ✓ 什么你的我的，都是大家的。 (the 的 is needed after each term).
✗ 什么你的我的？ read as a real question → it is a dismissal: you do not answer it with information.