anyone transpose a in this formula to make it the subject?
A = h x (a + b)/2
I assume the "x" is a multiplication symbol? If so, please don't use it. It looks too much like the variable x.
$\displaystyle A = h \cdot \frac{a + b}{2}$
$\displaystyle 2A = h(a + b)$
$\displaystyle 2A = ha + hb$
$\displaystyle ha = 2A - hb$
$\displaystyle a = \frac{2A - hb}{h}$
Then if you like
$\displaystyle a = \frac{2A}{h} - b$
-Dan