Question 176199
Just solve the function for a:


{{{h = 0.9(200 - a)}}}


Divide by 0.9


{{{h/0.9 = 200 - a}}}


Add -200 to both sides:


{{{h/0.9 - 200 = -a}}}


Multiply by -1:


{{{-h/0.9 + 200 = a}}}


{{{200 - h/0.9 = a}}}


{{{a = 200 - h/0.9}}}


Now just put 27 in place of h and do the arithmetic.