Hello, russellw!
$\displaystyle \text{Solve for }A\!:\;\;H \;=\;\frac{\dfrac{0.001221A}{5} - 0.16}{0.0062}$
$\displaystyle \text{We have: }\;\frac{\dfrac{0.001221A}{5} - 0.16}{0.0062}\;=\;H$
$\displaystyle \text{Multiply both sides by }0.0062\!:\;\;\frac{0.001221A}{5} - 0.16 \;=\;0.0062H$
$\displaystyle \text{Add 0.16 to both sides: }\;\frac{0.001221A}{5} \;=\;0.0062H + 0.16$
$\displaystyle \text{Multiply both sides by }5:\;\;0.001221A \;=\;0.031H + 0.8$
$\displaystyle \text{Divide by }0.001221\!:\;\;A \;=\;\frac{0.031H + 0.8}{0.001221} $