Step 1:
$9x^2+4y^2=20$
The above equation is dividing by $20$ we get
$\Large\frac{x^2}{\Large\frac{20}{9}}+\large\frac{y^2}{5}$$=1$
$a^2=5,b^2=\large\frac{20}{9}$
$\Rightarrow a=\sqrt 5,b=\large\frac{2\sqrt 5}{3}$
Step 2:
Length of major axis=$2a=2\sqrt 5$
Length of minor axis=$2b=\large\frac{4\sqrt 5}{3}$
Equation of major axis $x=0$
Equation of minor axis $y=0$