To solve for h, we must isolate it in one side of the equation. So we start here:
[tex]f=\frac{1}{4}(g+h-k)[/tex]All operations must be done in both sides, so the euqality is maintained. We can start by multiplying both sides by 4, which wil remove the fraction:
[tex]\begin{gathered} 4\cdot f=4\cdot\frac{1}{4}(g+h-k) \\ 4f=g+h-k \end{gathered}[/tex]Now, let's invert the equation, so that h is on the left side:
[tex]g+h-k=4f[/tex]Now we can substract g from both sides:
[tex]\begin{gathered} g+h-k-g=4f-g \\ g-g+h-k=4f-g \\ h-k=4f-g \end{gathered}[/tex]Finally, we can add k in both sides:
[tex]\begin{gathered} h-k+k=4f-g+k \\ h=4f-g+k \end{gathered}[/tex]And so we solved for h.