Kabir solves x + 2 = 7 in one problem and gets x = 5

Why

Kabir's assumption comes from a completely reasonable habit — a person's name usually refers to the same person wherever it's mentioned, so it feels natural to expect the letter x to carry a fixed identity the same way, wherever it shows up. But x isn't a name for a particular fixed number; it's a placeholder that stands for WHATEVER number makes THAT PARTICULAR equation true, and a different equation is free to have its own, completely unrelated value hiding behind the same letter. Solve the new equation on its own terms: x + 3 = 10 means x = 10 − 3 = 7, not 5. Check: does 5 + 3 actually equal 10? No, it's 8. Does 7 + 3 equal 10? Yes. The x from the earlier problem has nothing to do with this one — they just happen to share a letter, the way two different students might both be called Rahul without being the same person. Test: solve x + 1 = 2 (giving x=1) and then x × 10 = 100 (giving x=10) side by side — two totally different values, both correctly called x, in two unconnected equations. No, this is a new equation with its own x: a variable's value is defined fresh by whichever equation it appears in, not carried forward from an earlier, unrelated one.