The pH of a solution is 5. Find [H⁺].

$[$$H$$+$$]$ for pH 5
Answer: $[\text{H}^+]=10^{-\text{pH}}=10^{-5}\ \text{M}$.
Method: pH is defined as the negative base-10 logarithm of hydrogen ion concentration for aqueous solutions at typical conditions. Reverse the log by exponentiation. If the solution is very dilute or not at 25 °C, activity effects may matter, but standard NEET treatment assumes ideality. You can check pOH as $14-\text{pH}=9$ at 25 °C, then $[\text{OH}^-]=10^{-9}\ \text{M}$, and $K_w=[\text{H}^+][\text{OH}^-]=10^{-14}$. All relations are internally consistent.