We are given the equations
h = -0.2d² + 2.25d
-d + 6h = 21.77
Solving for d in the second equation:
-d + 6h = 21.77
d = 6h - 21.77
Substituting to the first equation:
h = -0.2(6h - 21.77)² + 2.25(6h - 21.77)
The value of h can then be solved with is
h = 3.9968
so
d = 2.2108