Question 883427
You can type | on a keyboard using Shift+\.


Also, it helps to be clearer with typing expressions because we don't know if you mean *[tex \large ||x|| = \frac{2}{3}x^2] or *[tex \large ||x|| = \frac{2}{3x^2}] or if *[tex \large y = \frac{2}{3}x] or *[tex \large y = \frac{2}{3x}]. Insert parentheses so that your expressions are unambiguous. In any case, replace y with the correct expression and solve.